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[PATCH 03/10] Make sure published XIDs are persistent 2+ messages / 2 participants [nested] [flat]
* [PATCH 03/10] Make sure published XIDs are persistent @ 2021-03-08 06:43 Kyotaro Horiguchi <[email protected]> 0 siblings, 0 replies; 2+ messages in thread From: Kyotaro Horiguchi @ 2021-03-08 06:43 UTC (permalink / raw) pg_xact_status() premises that XIDs obtained by pg_current_xact_id(_if_assigned)() are persistent beyond a crash. But XIDs are not guaranteed to go beyond WAL buffers before commit and thus XIDs may vanish if server crashes before commit. This patch guarantees the XID shown by the functions to be flushed out to disk. Copied from: https://www.postgresql.org/message-id/20210308.173242.463790587797836129.horikyota.ntt%40gmail.com --- src/backend/access/transam/xact.c | 55 +++++++++++++++++++++++++------ src/backend/access/transam/xlog.c | 2 +- src/backend/utils/adt/xid8funcs.c | 12 ++++++- src/include/access/xact.h | 3 +- 4 files changed, 59 insertions(+), 13 deletions(-) diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 6395a9b240..38e978d238 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -201,7 +201,7 @@ typedef struct TransactionStateData int prevSecContext; /* previous SecurityRestrictionContext */ bool prevXactReadOnly; /* entry-time xact r/o state */ bool startedInRecovery; /* did we start in recovery? */ - bool didLogXid; /* has xid been included in WAL record? */ + XLogRecPtr minLSN; /* LSN needed to reach to record the xid */ int parallelModeLevel; /* Enter/ExitParallelMode counter */ bool chain; /* start a new block after this one */ bool assigned; /* assigned to top-level XID */ @@ -520,14 +520,46 @@ GetCurrentFullTransactionIdIfAny(void) * MarkCurrentTransactionIdLoggedIfAny * * Remember that the current xid - if it is assigned - now has been wal logged. + * + * upto is the LSN up to which we need to flush WAL to ensure the current xid + * to be persistent. See EnsureCurrentTransactionIdLogged(). */ void -MarkCurrentTransactionIdLoggedIfAny(void) +MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto) { - if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId)) - CurrentTransactionState->didLogXid = true; + if (FullTransactionIdIsValid(CurrentTransactionState->fullTransactionId) && + XLogRecPtrIsInvalid(CurrentTransactionState->minLSN)) + CurrentTransactionState->minLSN = upto; } +/* + * EnsureCurrentTransactionIdLogged + * + * Make sure that the current top XID is WAL-logged. + */ +void +EnsureTopTransactionIdLogged(void) +{ + /* + * We need at least one WAL record for the current top transaction to be + * flushed out. Write one if we don't have one yet. + */ + if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN)) + { + xl_xact_assignment xlrec; + + xlrec.xtop = XidFromFullTransactionId(XactTopFullTransactionId); + Assert(TransactionIdIsValid(xlrec.xtop)); + xlrec.nsubxacts = 0; + + XLogBeginInsert(); + XLogRegisterData((char *) &xlrec, MinSizeOfXactAssignment); + TopTransactionStateData.minLSN = + XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT); + } + + XLogFlush(TopTransactionStateData.minLSN); +} /* * GetStableLatestTransactionId @@ -616,14 +648,14 @@ AssignTransactionId(TransactionState s) * When wal_level=logical, guarantee that a subtransaction's xid can only * be seen in the WAL stream if its toplevel xid has been logged before. * If necessary we log an xact_assignment record with fewer than - * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if didLogXid isn't set + * PGPROC_MAX_CACHED_SUBXIDS. Note that it is fine if minLSN isn't set * for a transaction even though it appears in a WAL record, we just might * superfluously log something. That can happen when an xid is included * somewhere inside a wal record, but not in XLogRecord->xl_xid, like in * xl_standby_locks. */ if (isSubXact && XLogLogicalInfoActive() && - !TopTransactionStateData.didLogXid) + XLogRecPtrIsInvalid(TopTransactionStateData.minLSN)) log_unknown_top = true; /* @@ -693,6 +725,7 @@ AssignTransactionId(TransactionState s) log_unknown_top) { xl_xact_assignment xlrec; + XLogRecPtr endptr; /* * xtop is always set by now because we recurse up transaction @@ -707,11 +740,13 @@ AssignTransactionId(TransactionState s) XLogRegisterData((char *) unreportedXids, nUnreportedXids * sizeof(TransactionId)); - (void) XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT); + endptr = XLogInsert(RM_XACT_ID, XLOG_XACT_ASSIGNMENT); nUnreportedXids = 0; - /* mark top, not current xact as having been logged */ - TopTransactionStateData.didLogXid = true; + + /* set minLSN of top, not of current xact if not yet */ + if (XLogRecPtrIsInvalid(TopTransactionStateData.minLSN)) + TopTransactionStateData.minLSN = endptr; } } } @@ -2022,7 +2057,7 @@ StartTransaction(void) * initialize reported xid accounting */ nUnreportedXids = 0; - s->didLogXid = false; + s->minLSN = InvalidXLogRecPtr; /* * must initialize resource-management stuff first diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 04192b7add..0183589b4d 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -1171,7 +1171,7 @@ XLogInsertRecord(XLogRecData *rdata, */ WALInsertLockRelease(); - MarkCurrentTransactionIdLoggedIfAny(); + MarkCurrentTransactionIdLoggedIfAny(EndPos); END_CRIT_SECTION(); diff --git a/src/backend/utils/adt/xid8funcs.c b/src/backend/utils/adt/xid8funcs.c index cc2b4ac797..992482f8c8 100644 --- a/src/backend/utils/adt/xid8funcs.c +++ b/src/backend/utils/adt/xid8funcs.c @@ -357,6 +357,8 @@ bad_format: Datum pg_current_xact_id(PG_FUNCTION_ARGS) { + FullTransactionId xid; + /* * Must prevent during recovery because if an xid is not assigned we try * to assign one, which would fail. Programs already rely on this function @@ -365,7 +367,12 @@ pg_current_xact_id(PG_FUNCTION_ARGS) */ PreventCommandDuringRecovery("pg_current_xact_id()"); - PG_RETURN_FULLTRANSACTIONID(GetTopFullTransactionId()); + xid = GetTopFullTransactionId(); + + /* the XID is going to be published, make sure it is psersistent */ + EnsureTopTransactionIdLogged(); + + PG_RETURN_FULLTRANSACTIONID(xid); } /* @@ -380,6 +387,9 @@ pg_current_xact_id_if_assigned(PG_FUNCTION_ARGS) if (!FullTransactionIdIsValid(topfxid)) PG_RETURN_NULL(); + /* the XID is going to be published, make sure it is psersistent */ + EnsureTopTransactionIdLogged(); + PG_RETURN_FULLTRANSACTIONID(topfxid); } diff --git a/src/include/access/xact.h b/src/include/access/xact.h index 34cfaf542c..a61e4d6da5 100644 --- a/src/include/access/xact.h +++ b/src/include/access/xact.h @@ -386,7 +386,8 @@ extern FullTransactionId GetTopFullTransactionId(void); extern FullTransactionId GetTopFullTransactionIdIfAny(void); extern FullTransactionId GetCurrentFullTransactionId(void); extern FullTransactionId GetCurrentFullTransactionIdIfAny(void); -extern void MarkCurrentTransactionIdLoggedIfAny(void); +extern void MarkCurrentTransactionIdLoggedIfAny(XLogRecPtr upto); +extern void EnsureTopTransactionIdLogged(void); extern bool SubTransactionIsActive(SubTransactionId subxid); extern CommandId GetCurrentCommandId(bool used); extern void SetParallelStartTimestamps(TimestampTz xact_ts, TimestampTz stmt_ts); -- 2.17.0 --0qVF/w3MHQqLSynd Content-Type: text/x-diff; charset=us-ascii Content-Disposition: attachment; filename="0004-wal_compression_method-default-to-zlib.patch" ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: BitmapHeapScan streaming read user and prelim refactoring @ 2024-02-14 04:34 Mark Dilger <[email protected]> 0 siblings, 0 replies; 2+ messages in thread From: Mark Dilger @ 2024-02-14 04:34 UTC (permalink / raw) To: Melanie Plageman <[email protected]>; +Cc: pgsql-hackers; Andres Freund <[email protected]>; Thomas Munro <[email protected]>; Heikki Linnakangas <[email protected]>; Nazir Bilal Yavuz <[email protected]> > On Feb 13, 2024, at 3:11 PM, Melanie Plageman <[email protected]> wrote: Thanks for the patch... > Attached is a patch set which refactors BitmapHeapScan such that it > can use the streaming read API [1]. It also resolves the long-standing > FIXME in the BitmapHeapScan code suggesting that the skip fetch > optimization should be pushed into the table AMs. Additionally, it > moves table scan initialization to after the index scan and bitmap > initialization. > > patches 0001-0002 are assorted cleanup needed later in the set. > patches 0003 moves the table scan initialization to after bitmap creation > patch 0004 is, I think, a bug fix. see [2]. > patches 0005-0006 push the skip fetch optimization into the table AMs > patches 0007-0009 change the control flow of BitmapHeapNext() to match > that required by the streaming read API > patch 0010 is the streaming read code not yet in master > patch 0011 is the actual bitmapheapscan streaming read user. > > patches 0001-0009 apply on top of master but 0010 and 0011 must be > applied on top of a commit before a 21d9c3ee4ef74e2 (until a rebased > version of the streaming read API is on the mailing list). I followed your lead and applied them to 6a8ffe812d194ba6f4f26791b6388a4837d17d6c. `make check` worked fine, though I expect you know that already. > The caveat is that these patches introduce breaking changes to two > table AM functions for bitmapheapscan: table_scan_bitmap_next_block() > and table_scan_bitmap_next_tuple(). You might want an independent perspective on how much of a hassle those breaking changes are, so I took a stab at that. Having written a custom proprietary TAM for postgresql 15 here at EDB, and having ported it and released it for postgresql 16, I thought I'd try porting it to the the above commit with your patches. Even without your patches, I already see breaking changes coming from commit f691f5b80a85c66d715b4340ffabb503eb19393e, which creates a similar amount of breakage for me as does your patches. Dealing with the combined breakage might amount to a day of work, including testing, half of which I think I've already finished. In other words, it doesn't seem like a big deal. Were postgresql 17 shaping up to be compatible with TAMs written for 16, your patch would change that qualitatively, but since things are already incompatible, I think you're in the clear. > A TBMIterateResult used to be threaded through both of these functions > and used in BitmapHeapNext(). This patch set removes all references to > TBMIterateResults from BitmapHeapNext. Because the streaming read API > requires the callback to specify the next block, BitmapHeapNext() can > no longer pass a TBMIterateResult to table_scan_bitmap_next_block(). > > More subtly, table_scan_bitmap_next_block() used to return false if > there were no more visible tuples on the page or if the block that was > requested was not valid. With these changes, > table_scan_bitmap_next_block() will only return false when the bitmap > has been exhausted and the scan can end. In order to use the streaming > read API, the user must be able to request the blocks it needs without > requiring synchronous feedback per block. Thus, this table AM function > must change its meaning. > > I think the way the patches are split up could be improved. I will > think more about this. There are also probably a few mistakes with > which comments are updated in which patches in the set. I look forward to the next version of the patch set. Thanks again for working on this. — Mark Dilger EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2024-02-14 04:34 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2021-03-08 06:43 [PATCH 03/10] Make sure published XIDs are persistent Kyotaro Horiguchi <[email protected]> 2024-02-14 04:34 Re: BitmapHeapScan streaming read user and prelim refactoring Mark Dilger <[email protected]>
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