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[PATCH v49 5/7] Doc part of shared-memory based stats collector.
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* [PATCH v49 5/7] Doc part of shared-memory based stats collector.
@ 2020-03-19 06:11 Kyotaro Horiguchi <[email protected]>
  0 siblings, 0 replies; 2+ messages in thread

From: Kyotaro Horiguchi @ 2020-03-19 06:11 UTC (permalink / raw)

---
 doc/src/sgml/catalogs.sgml          |   6 +-
 doc/src/sgml/config.sgml            |  27 +++---
 doc/src/sgml/high-availability.sgml |  13 +--
 doc/src/sgml/monitoring.sgml        | 127 +++++++++++++---------------
 doc/src/sgml/ref/pg_dump.sgml       |   9 +-
 5 files changed, 86 insertions(+), 96 deletions(-)

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index b1de6d0674..0ef684d4d0 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -9261,9 +9261,9 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
   <para>
    <xref linkend="view-table"/> lists the system views described here.
    More detailed documentation of each view follows below.
-   There are some additional views that provide access to the results of
-   the statistics collector; they are described in <xref
-   linkend="monitoring-stats-views-table"/>.
+   There are some additional views that provide access to the activity
+   statistics; they are described in
+   <xref linkend="monitoring-stats-views-table"/>.
   </para>
 
   <para>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 967de73596..753b1ab6f9 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -7375,11 +7375,11 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
     <title>Run-time Statistics</title>
 
     <sect2 id="runtime-config-statistics-collector">
-     <title>Query and Index Statistics Collector</title>
+     <title>Query and Index Activity Statistics</title>
 
      <para>
-      These parameters control server-wide statistics collection features.
-      When statistics collection is enabled, the data that is produced can be
+      These parameters control server-wide activity statistics features.
+      When activity statistics is enabled, the data that is produced can be
       accessed via the <structname>pg_stat</structname> and
       <structname>pg_statio</structname> family of system views.
       Refer to <xref linkend="monitoring"/> for more information.
@@ -7395,14 +7395,13 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </term>
       <listitem>
        <para>
-        Enables the collection of information on the currently
-        executing command of each session, along with the time when
-        that command began execution. This parameter is on by
-        default. Note that even when enabled, this information is not
-        visible to all users, only to superusers and the user owning
-        the session being reported on, so it should not represent a
-        security risk.
-        Only superusers can change this setting.
+        Enables activity tracking on the currently executing command of
+        each session, along with the time when that command began
+        execution. This parameter is on by default. Note that even when
+        enabled, this information is not visible to all users, only to
+        superusers and the user owning the session being reported on, so it
+        should not represent a security risk.  Only superusers can change this
+        setting.
        </para>
       </listitem>
      </varlistentry>
@@ -7433,9 +7432,9 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </term>
       <listitem>
        <para>
-        Enables collection of statistics on database activity.
+        Enables tracking of database activity.
         This parameter is on by default, because the autovacuum
-        daemon needs the collected information.
+        daemon needs the activity information.
         Only superusers can change this setting.
        </para>
       </listitem>
@@ -8533,7 +8532,7 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       <listitem>
        <para>
         Specifies the fraction of the total number of heap tuples counted in
-        the previous statistics collection that can be inserted without
+        the previously collected statistics that can be inserted without
         incurring an index scan at the <command>VACUUM</command> cleanup stage.
         This setting currently applies to B-tree indexes only.
        </para>
diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml
index f49f5c0108..45095857eb 100644
--- a/doc/src/sgml/high-availability.sgml
+++ b/doc/src/sgml/high-availability.sgml
@@ -2217,12 +2217,13 @@ HINT:  You can then restart the server after making the necessary configuration
    </para>
 
    <para>
-    The statistics collector is active during recovery. All scans, reads, blocks,
-    index usage, etc., will be recorded normally on the standby. Replayed
-    actions will not duplicate their effects on primary, so replaying an
-    insert will not increment the Inserts column of pg_stat_user_tables.
-    The stats file is deleted at the start of recovery, so stats from primary
-    and standby will differ; this is considered a feature, not a bug.
+    The activity statistics is collected during recovery. All scans, reads,
+    blocks, index usage, etc., will be recorded normally on the
+    standby. Replayed actions will not duplicate their effects on primary, so
+    replaying an insert will not increment the Inserts column of
+    pg_stat_user_tables.  The activity statistics is reset at the start of
+    recovery, so stats from primary and standby will differ; this is
+    considered a feature, not a bug.
    </para>
 
    <para>
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 53692c0020..d4af6079aa 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -22,7 +22,7 @@
   <para>
    Several tools are available for monitoring database activity and
    analyzing performance.  Most of this chapter is devoted to describing
-   <productname>PostgreSQL</productname>'s statistics collector,
+   <productname>PostgreSQL</productname>'s activity statistics,
    but one should not neglect regular Unix monitoring programs such as
    <command>ps</command>, <command>top</command>, <command>iostat</command>, and <command>vmstat</command>.
    Also, once one has identified a
@@ -53,7 +53,6 @@ postgres  15554  0.0  0.0  57536  1184 ?        Ss   18:02   0:00 postgres: back
 postgres  15555  0.0  0.0  57536   916 ?        Ss   18:02   0:00 postgres: checkpointer
 postgres  15556  0.0  0.0  57536   916 ?        Ss   18:02   0:00 postgres: walwriter
 postgres  15557  0.0  0.0  58504  2244 ?        Ss   18:02   0:00 postgres: autovacuum launcher
-postgres  15558  0.0  0.0  17512  1068 ?        Ss   18:02   0:00 postgres: stats collector
 postgres  15582  0.0  0.0  58772  3080 ?        Ss   18:04   0:00 postgres: joe runbug 127.0.0.1 idle
 postgres  15606  0.0  0.0  58772  3052 ?        Ss   18:07   0:00 postgres: tgl regression [local] SELECT waiting
 postgres  15610  0.0  0.0  58772  3056 ?        Ss   18:07   0:00 postgres: tgl regression [local] idle in transaction
@@ -65,9 +64,8 @@ postgres  15610  0.0  0.0  58772  3056 ?        Ss   18:07   0:00 postgres: tgl
    primary server process.  The command arguments
    shown for it are the same ones used when it was launched.  The next five
    processes are background worker processes automatically launched by the
-   primary process.  (The <quote>stats collector</quote> process will not be present
-   if you have set the system not to start the statistics collector; likewise
-   the <quote>autovacuum launcher</quote> process can be disabled.)
+   primary process.  (The <quote>autovacuum launcher</quote> process will not
+   be present if you have set the system not to start it.)
    Each of the remaining
    processes is a server process handling one client connection.  Each such
    process sets its command line display in the form
@@ -130,20 +128,21 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
  </sect1>
 
  <sect1 id="monitoring-stats">
-  <title>The Statistics Collector</title>
+  <title>The Activity Statistics</title>
 
   <indexterm zone="monitoring-stats">
    <primary>statistics</primary>
   </indexterm>
 
   <para>
-   <productname>PostgreSQL</productname>'s <firstterm>statistics collector</firstterm>
-   is a subsystem that supports collection and reporting of information about
-   server activity.  Presently, the collector can count accesses to tables
-   and indexes in both disk-block and individual-row terms.  It also tracks
-   the total number of rows in each table, and information about vacuum and
-   analyze actions for each table.  It can also count calls to user-defined
-   functions and the total time spent in each one.
+   <productname>PostgreSQL</productname>'s <firstterm>activity
+   statistics</firstterm> is a subsystem that supports tracking and reporting
+   of information about server activity.  Presently, the activity statistics
+   tracks the count of accesses to tables and indexes in both disk-block and
+   individual-row terms.  It also tracks the total number of rows in each
+   table, and information about vacuum and analyze actions for each table.  It
+   can also track calls to user-defined functions and the total time spent in
+   each one.
   </para>
 
   <para>
@@ -151,15 +150,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
    information about exactly what is going on in the system right now, such as
    the exact command currently being executed by other server processes, and
    which other connections exist in the system.  This facility is independent
-   of the collector process.
+   of the activity statistics.
   </para>
 
  <sect2 id="monitoring-stats-setup">
-  <title>Statistics Collection Configuration</title>
+  <title>Activity Statistics Configuration</title>
 
   <para>
-   Since collection of statistics adds some overhead to query execution,
-   the system can be configured to collect or not collect information.
+   Since tracking for the activity statistics adds some overhead to query
+   execution, the system can be configured to track or not track activity.
    This is controlled by configuration parameters that are normally set in
    <filename>postgresql.conf</filename>.  (See <xref linkend="runtime-config"/> for
    details about setting configuration parameters.)
@@ -172,7 +171,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
 
   <para>
    The parameter <xref linkend="guc-track-counts"/> controls whether
-   statistics are collected about table and index accesses.
+   to track activity about table and index accesses.
   </para>
 
   <para>
@@ -196,18 +195,11 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
   </para>
 
   <para>
-   The statistics collector transmits the collected information to other
-   <productname>PostgreSQL</productname> processes through temporary files.
-   These files are stored in the directory named by the
-   <xref linkend="guc-stats-temp-directory"/> parameter,
-   <filename>pg_stat_tmp</filename> by default.
-   For better performance, <varname>stats_temp_directory</varname> can be
-   pointed at a RAM-based file system, decreasing physical I/O requirements.
-   When the server shuts down cleanly, a permanent copy of the statistics
-   data is stored in the <filename>pg_stat</filename> subdirectory, so that
-   statistics can be retained across server restarts.  When recovery is
-   performed at server start (e.g., after immediate shutdown, server crash,
-   and point-in-time recovery), all statistics counters are reset.
+   down cleanly, a permanent copy of the statistics data is stored in
+   the <filename>pg_stat</filename> subdirectory, so that statistics can be
+   retained across server restarts.  When recovery is performed at server
+   start (e.g. after immediate shutdown, server crash, and point-in-time
+   recovery), all statistics counters are reset.
   </para>
 
  </sect2>
@@ -220,48 +212,46 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
    linkend="monitoring-stats-dynamic-views-table"/>, are available to show
    the current state of the system. There are also several other
    views, listed in <xref
-   linkend="monitoring-stats-views-table"/>, available to show the results
-   of statistics collection.  Alternatively, one can
-   build custom views using the underlying statistics functions, as discussed
-   in <xref linkend="monitoring-stats-functions"/>.
+   linkend="monitoring-stats-views-table"/>, available to show the activity
+   statistics.  Alternatively, one can build custom views using the underlying
+   statistics functions, as discussed in
+   <xref linkend="monitoring-stats-functions"/>.
   </para>
 
   <para>
-   When using the statistics to monitor collected data, it is important
-   to realize that the information does not update instantaneously.
-   Each individual server process transmits new statistical counts to
-   the collector just before going idle; so a query or transaction still in
-   progress does not affect the displayed totals.  Also, the collector itself
-   emits a new report at most once per <varname>PGSTAT_STAT_INTERVAL</varname>
-   milliseconds (500 ms unless altered while building the server).  So the
-   displayed information lags behind actual activity.  However, current-query
-   information collected by <varname>track_activities</varname> is
-   always up-to-date.
+   When using the activity statistics, it is important to realize that the
+   information does not update instantaneously.  Each individual server writes
+   out new statistical counts just before going idle, not frequent than once
+   per <varname>PGSTAT_STAT_INTERVAL</varname> milliseconds (1 second unless
+   altered while building the server); so a query or transaction still in
+   progress does not affect the displayed totals.  However, current-query
+   information tracked by <varname>track_activities</varname> is always
+   up-to-date.
   </para>
 
   <para>
    Another important point is that when a server process is asked to display
-   any of these statistics, it first fetches the most recent report emitted by
-   the collector process and then continues to use this snapshot for all
-   statistical views and functions until the end of its current transaction.
-   So the statistics will show static information as long as you continue the
-   current transaction.  Similarly, information about the current queries of
-   all sessions is collected when any such information is first requested
-   within a transaction, and the same information will be displayed throughout
-   the transaction.
-   This is a feature, not a bug, because it allows you to perform several
-   queries on the statistics and correlate the results without worrying that
-   the numbers are changing underneath you.  But if you want to see new
-   results with each query, be sure to do the queries outside any transaction
-   block.  Alternatively, you can invoke
+   any of these statistics, it first reads the current statistics and then
+   continues to use this snapshot for all statistical views and functions
+   until the end of its current transaction.  So the statistics will show
+   static information as long as you continue the current transaction.
+   Similarly, information about the current queries of all sessions is tracked
+   when any such information is first requested within a transaction, and the
+   same information will be displayed throughout the transaction.  This is a
+   feature, not a bug, because it allows you to perform several queries on the
+   statistics and correlate the results without worrying that the numbers are
+   changing underneath you.  But if you want to see new results with each
+   query, be sure to do the queries outside any transaction block.
+   Alternatively, you can invoke
    <function>pg_stat_clear_snapshot</function>(), which will discard the
    current transaction's statistics snapshot (if any).  The next use of
    statistical information will cause a new snapshot to be fetched.
   </para>
-
+  
   <para>
-   A transaction can also see its own statistics (as yet untransmitted to the
-   collector) in the views <structname>pg_stat_xact_all_tables</structname>,
+   A transaction can also see its own statistics (as yet unwritten to the
+   server-wide activity statistics) in the
+   views <structname>pg_stat_xact_all_tables</structname>,
    <structname>pg_stat_xact_sys_tables</structname>,
    <structname>pg_stat_xact_user_tables</structname>, and
    <structname>pg_stat_xact_user_functions</structname>.  These numbers do not act as
@@ -643,7 +633,7 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
    kernel's I/O cache, and might therefore still be fetched without
    requiring a physical read. Users interested in obtaining more
    detailed information on <productname>PostgreSQL</productname> I/O behavior are
-   advised to use the <productname>PostgreSQL</productname> statistics collector
+   advised to use the <productname>PostgreSQL</productname> activity statistics
    in combination with operating system utilities that allow insight
    into the kernel's handling of I/O.
   </para>
@@ -1080,10 +1070,6 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       <entry><literal>LogicalLauncherMain</literal></entry>
       <entry>Waiting in main loop of logical replication launcher process.</entry>
      </row>
-     <row>
-      <entry><literal>PgStatMain</literal></entry>
-      <entry>Waiting in main loop of statistics collector process.</entry>
-     </row>
      <row>
       <entry><literal>RecoveryWalStream</literal></entry>
       <entry>Waiting in main loop of startup process for WAL to arrive, during
@@ -1838,6 +1824,10 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
     </thead>
 
     <tbody>
+     <row>
+      <entry><literal>ActivityStatistics</literal></entry>
+      <entry>Waiting to write out activity statistics to shared memory.</entry>
+     </row>
      <row>
       <entry><literal>AddinShmemInit</literal></entry>
       <entry>Waiting to manage an extension's space allocation in shared
@@ -6061,9 +6051,10 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
      <entry><literal>performing final cleanup</literal></entry>
      <entry>
        <command>VACUUM</command> is performing final cleanup.  During this phase,
-       <command>VACUUM</command> will vacuum the free space map, update statistics
-       in <literal>pg_class</literal>, and report statistics to the statistics
-       collector.  When this phase is completed, <command>VACUUM</command> will end.
+       <command>VACUUM</command> will vacuum the free space map, update
+       statistics in <literal>pg_class</literal>, and system-wide activity
+       statistics.  When this phase is completed, <command>VACUUM</command>
+       will end.
      </entry>
     </row>
    </tbody>
diff --git a/doc/src/sgml/ref/pg_dump.sgml b/doc/src/sgml/ref/pg_dump.sgml
index bcbb7a25fb..1fa59a2fdf 100644
--- a/doc/src/sgml/ref/pg_dump.sgml
+++ b/doc/src/sgml/ref/pg_dump.sgml
@@ -1280,11 +1280,10 @@ PostgreSQL documentation
   </para>
 
   <para>
-   The database activity of <application>pg_dump</application> is
-   normally collected by the statistics collector.  If this is
-   undesirable, you can set parameter <varname>track_counts</varname>
-   to false via <envar>PGOPTIONS</envar> or the <literal>ALTER
-   USER</literal> command.
+   The database activity of <application>pg_dump</application> is normally
+   collected.  If this is undesirable, you can set
+   parameter <varname>track_counts</varname> to false
+   via <envar>PGOPTIONS</envar> or the <literal>ALTER USER</literal> command.
   </para>
 
  </refsect1>
-- 
2.27.0


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Content-Type: Text/X-Patch; charset=us-ascii
Content-Transfer-Encoding: 7bit
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 filename="v49-0006-Remove-the-GUC-stats_temp_directory.patch"



^ permalink  raw  reply  [nested|flat] 2+ messages in thread

* [PATCH v20 6/6] Preserve visibility information of the concurrent data changes.
@ 2025-08-30 17:40 Álvaro Herrera <[email protected]>
  0 siblings, 0 replies; 2+ messages in thread

From: Álvaro Herrera @ 2025-08-30 17:40 UTC (permalink / raw)

As explained in the commit message of the preceding patch of the series, the
data changes done by applications while REPACK CONCURRENTLY is copying the
table contents to a new file are decoded from WAL and eventually also applied
to the new file. To reduce the complexity a little bit, the preceding patch
uses the current transaction (i.e. transaction opened by the REPACK command)
to execute those INSERT, UPDATE and DELETE commands.

However, REPACK is not expected to change visibility of tuples. Therefore,
this patch fixes the handling of the "concurrent data changes". It ensures
that tuples written into the new table have the same XID and command ID (CID)
as they had in the old table.

To "replay" an UPDATE or DELETE command on the new table, we need the
appropriate snapshot to find the previous tuple version in the new table. The
(historic) snapshot we used to decode the UPDATE / DELETE should (by
definition) see the state of the catalog prior to that UPDATE / DELETE. Thus
we can use the same snapshot to find the "old tuple" for UPDATE / DELETE in
the new table if:

1) REPACK CONCURRENTLY preserves visibility information of all tuples - that's
the purpose of this part of the patch series.

2) The table being REPACKed is treated as a system catalog by all transactions
that modify its data. This ensures that reorderbuffer.c generates a new
snapshot for each data change in the table.

We ensure 2) by maintaining a shared hashtable of tables being REPACKed
CONCURRENTLY and by adjusting the RelationIsAccessibleInLogicalDecoding()
macro so it checks this hashtable. (The corresponding flag is also added to
the relation cache, so that the shared hashtable does not have to be accessed
too often.) It's essential that after adding an entry to the hashtable we wait
for completion of all the transactions that might have started to modify our
table before our entry has was added. We achieve that by upgrading our lock on
the table to ShareLock temporarily: as soon as we acquire it, no DML command
should be running on the table. (This lock upgrade shouldn't cause any
deadlock because we care to not hold a lock on other objects at the same
time.)

As long as we preserve the tuple visibility information (which includes XID),
it's important to avoid logical decoding of the WAL generated by DMLs on the
new table: the logical decoding subsystem probably does not expect that the
incoming WAL records contain XIDs of an already decoded transactions. (And of
course, repeated decoding would be wasted effort.)

Author: Antonin Houska <[email protected]>
Author: Mikhail Nikalayeu <[email protected]> (small changes)
---
 src/backend/access/common/toast_internals.c   |   3 +-
 src/backend/access/heap/heapam.c              |  51 ++-
 src/backend/access/heap/heapam_handler.c      |  23 +-
 src/backend/access/transam/xact.c             |  52 +++
 src/backend/commands/cluster.c                | 400 ++++++++++++++++--
 src/backend/replication/logical/decode.c      |  28 +-
 src/backend/replication/logical/snapbuild.c   |  22 +-
 .../pgoutput_repack/pgoutput_repack.c         |  68 ++-
 src/backend/storage/ipc/ipci.c                |   2 +
 .../utils/activity/wait_event_names.txt       |   1 +
 src/backend/utils/cache/inval.c               |  21 +
 src/backend/utils/cache/relcache.c            |   4 +
 src/include/access/heapam.h                   |  12 +-
 src/include/access/xact.h                     |   2 +
 src/include/commands/cluster.h                |  22 +
 src/include/storage/lwlocklist.h              |   1 +
 src/include/utils/inval.h                     |   2 +
 src/include/utils/rel.h                       |   7 +-
 src/include/utils/snapshot.h                  |   3 +
 .../injection_points/specs/repack.spec        |   4 -
 src/tools/pgindent/typedefs.list              |   1 +
 21 files changed, 635 insertions(+), 94 deletions(-)

diff --git a/src/backend/access/common/toast_internals.c b/src/backend/access/common/toast_internals.c
index a1d0eed8953..586eb42a137 100644
--- a/src/backend/access/common/toast_internals.c
+++ b/src/backend/access/common/toast_internals.c
@@ -320,7 +320,8 @@ toast_save_datum(Relation rel, Datum value,
 		memcpy(VARDATA(&chunk_data), data_p, chunk_size);
 		toasttup = heap_form_tuple(toasttupDesc, t_values, t_isnull);
 
-		heap_insert(toastrel, toasttup, mycid, options, NULL);
+		heap_insert(toastrel, toasttup, GetCurrentTransactionId(), mycid,
+					options, NULL);
 
 		/*
 		 * Create the index entry.  We cheat a little here by not using
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index f9a4fe3faed..fd17286cabe 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -2070,7 +2070,7 @@ ReleaseBulkInsertStatePin(BulkInsertState bistate)
 /*
  *	heap_insert		- insert tuple into a heap
  *
- * The new tuple is stamped with current transaction ID and the specified
+ * The new tuple is stamped with specified transaction ID and the specified
  * command ID.
  *
  * See table_tuple_insert for comments about most of the input flags, except
@@ -2086,15 +2086,16 @@ ReleaseBulkInsertStatePin(BulkInsertState bistate)
  * reflected into *tup.
  */
 void
-heap_insert(Relation relation, HeapTuple tup, CommandId cid,
-			int options, BulkInsertState bistate)
+heap_insert(Relation relation, HeapTuple tup, TransactionId xid,
+			CommandId cid, int options, BulkInsertState bistate)
 {
-	TransactionId xid = GetCurrentTransactionId();
 	HeapTuple	heaptup;
 	Buffer		buffer;
 	Buffer		vmbuffer = InvalidBuffer;
 	bool		all_visible_cleared = false;
 
+	Assert(TransactionIdIsValid(xid));
+
 	/* Cheap, simplistic check that the tuple matches the rel's rowtype. */
 	Assert(HeapTupleHeaderGetNatts(tup->t_data) <=
 		   RelationGetNumberOfAttributes(relation));
@@ -2176,8 +2177,15 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
 		/*
 		 * If this is a catalog, we need to transmit combo CIDs to properly
 		 * decode, so log that as well.
+		 *
+		 * HEAP_INSERT_NO_LOGICAL should be set when applying data changes
+		 * done by other transactions during REPACK CONCURRENTLY. In such a
+		 * case, the insertion should not be decoded at all - see
+		 * heap_decode(). (It's also set by raw_heap_insert() for TOAST, but
+		 * TOAST does not pass this test anyway.)
 		 */
-		if (RelationIsAccessibleInLogicalDecoding(relation))
+		if ((options & HEAP_INSERT_NO_LOGICAL) == 0 &&
+			RelationIsAccessibleInLogicalDecoding(relation))
 			log_heap_new_cid(relation, heaptup);
 
 		/*
@@ -2723,7 +2731,8 @@ heap_multi_insert(Relation relation, TupleTableSlot **slots, int ntuples,
 void
 simple_heap_insert(Relation relation, HeapTuple tup)
 {
-	heap_insert(relation, tup, GetCurrentCommandId(true), 0, NULL);
+	heap_insert(relation, tup, GetCurrentTransactionId(),
+				GetCurrentCommandId(true), 0, NULL);
 }
 
 /*
@@ -2780,11 +2789,11 @@ xmax_infomask_changed(uint16 new_infomask, uint16 old_infomask)
  */
 TM_Result
 heap_delete(Relation relation, ItemPointer tid,
-			CommandId cid, Snapshot crosscheck, bool wait,
-			TM_FailureData *tmfd, bool changingPart, bool wal_logical)
+			TransactionId xid, CommandId cid, Snapshot crosscheck, bool wait,
+			TM_FailureData *tmfd, bool changingPart,
+			bool wal_logical)
 {
 	TM_Result	result;
-	TransactionId xid = GetCurrentTransactionId();
 	ItemId		lp;
 	HeapTupleData tp;
 	Page		page;
@@ -2801,6 +2810,7 @@ heap_delete(Relation relation, ItemPointer tid,
 	bool		old_key_copied = false;
 
 	Assert(ItemPointerIsValid(tid));
+	Assert(TransactionIdIsValid(xid));
 
 	AssertHasSnapshotForToast(relation);
 
@@ -3097,8 +3107,12 @@ l1:
 		/*
 		 * For logical decode we need combo CIDs to properly decode the
 		 * catalog
+		 *
+		 * Like in heap_insert(), visibility is unchanged when called from
+		 * VACUUM FULL / CLUSTER.
 		 */
-		if (RelationIsAccessibleInLogicalDecoding(relation))
+		if (wal_logical &&
+			RelationIsAccessibleInLogicalDecoding(relation))
 			log_heap_new_cid(relation, &tp);
 
 		xlrec.flags = 0;
@@ -3217,11 +3231,12 @@ simple_heap_delete(Relation relation, ItemPointer tid)
 	TM_Result	result;
 	TM_FailureData tmfd;
 
-	result = heap_delete(relation, tid,
+	result = heap_delete(relation, tid, GetCurrentTransactionId(),
 						 GetCurrentCommandId(true), InvalidSnapshot,
 						 true /* wait for commit */ ,
 						 &tmfd, false,	/* changingPart */
 						 true /* wal_logical */ );
+
 	switch (result)
 	{
 		case TM_SelfModified:
@@ -3260,12 +3275,11 @@ simple_heap_delete(Relation relation, ItemPointer tid)
  */
 TM_Result
 heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
-			CommandId cid, Snapshot crosscheck, bool wait,
-			TM_FailureData *tmfd, LockTupleMode *lockmode,
+			TransactionId xid, CommandId cid, Snapshot crosscheck,
+			bool wait, TM_FailureData *tmfd, LockTupleMode *lockmode,
 			TU_UpdateIndexes *update_indexes, bool wal_logical)
 {
 	TM_Result	result;
-	TransactionId xid = GetCurrentTransactionId();
 	Bitmapset  *hot_attrs;
 	Bitmapset  *sum_attrs;
 	Bitmapset  *key_attrs;
@@ -3305,6 +3319,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
 				infomask2_new_tuple;
 
 	Assert(ItemPointerIsValid(otid));
+	Assert(TransactionIdIsValid(xid));
 
 	/* Cheap, simplistic check that the tuple matches the rel's rowtype. */
 	Assert(HeapTupleHeaderGetNatts(newtup->t_data) <=
@@ -4144,8 +4159,12 @@ l2:
 		/*
 		 * For logical decoding we need combo CIDs to properly decode the
 		 * catalog.
+		 *
+		 * Like in heap_insert(), visibility is unchanged when called from
+		 * VACUUM FULL / CLUSTER.
 		 */
-		if (RelationIsAccessibleInLogicalDecoding(relation))
+		if (wal_logical &&
+			RelationIsAccessibleInLogicalDecoding(relation))
 		{
 			log_heap_new_cid(relation, &oldtup);
 			log_heap_new_cid(relation, heaptup);
@@ -4511,7 +4530,7 @@ simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup,
 	TM_FailureData tmfd;
 	LockTupleMode lockmode;
 
-	result = heap_update(relation, otid, tup,
+	result = heap_update(relation, otid, tup, GetCurrentTransactionId(),
 						 GetCurrentCommandId(true), InvalidSnapshot,
 						 true /* wait for commit */ ,
 						 &tmfd, &lockmode, update_indexes,
diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index d03084768e0..b50f7dc9b9c 100644
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -253,7 +253,8 @@ heapam_tuple_insert(Relation relation, TupleTableSlot *slot, CommandId cid,
 	tuple->t_tableOid = slot->tts_tableOid;
 
 	/* Perform the insertion, and copy the resulting ItemPointer */
-	heap_insert(relation, tuple, cid, options, bistate);
+	heap_insert(relation, tuple, GetCurrentTransactionId(), cid, options,
+				bistate);
 	ItemPointerCopy(&tuple->t_self, &slot->tts_tid);
 
 	if (shouldFree)
@@ -276,7 +277,8 @@ heapam_tuple_insert_speculative(Relation relation, TupleTableSlot *slot,
 	options |= HEAP_INSERT_SPECULATIVE;
 
 	/* Perform the insertion, and copy the resulting ItemPointer */
-	heap_insert(relation, tuple, cid, options, bistate);
+	heap_insert(relation, tuple, GetCurrentTransactionId(), cid, options,
+				bistate);
 	ItemPointerCopy(&tuple->t_self, &slot->tts_tid);
 
 	if (shouldFree)
@@ -310,8 +312,8 @@ heapam_tuple_delete(Relation relation, ItemPointer tid, CommandId cid,
 	 * the storage itself is cleaning the dead tuples by itself, it is the
 	 * time to call the index tuple deletion also.
 	 */
-	return heap_delete(relation, tid, cid, crosscheck, wait, tmfd, changingPart,
-					   true);
+	return heap_delete(relation, tid, GetCurrentTransactionId(), cid,
+					   crosscheck, wait, tmfd, changingPart, true);
 }
 
 
@@ -329,7 +331,8 @@ heapam_tuple_update(Relation relation, ItemPointer otid, TupleTableSlot *slot,
 	slot->tts_tableOid = RelationGetRelid(relation);
 	tuple->t_tableOid = slot->tts_tableOid;
 
-	result = heap_update(relation, otid, tuple, cid, crosscheck, wait,
+	result = heap_update(relation, otid, tuple, GetCurrentTransactionId(),
+						 cid, crosscheck, wait,
 						 tmfd, lockmode, update_indexes, true);
 	ItemPointerCopy(&tuple->t_self, &slot->tts_tid);
 
@@ -2477,9 +2480,15 @@ reform_and_rewrite_tuple(HeapTuple tuple,
 		 * flag to skip logical decoding: as soon as REPACK CONCURRENTLY swaps
 		 * the relation files, it drops this relation, so no logical
 		 * replication subscription should need the data.
+		 *
+		 * It is also crucial to stamp the new record with the exact same xid
+		 * and cid, because the tuple must be visible to the snapshot of the
+		 * applied concurrent change later.
 		 */
-		heap_insert(NewHeap, copiedTuple, GetCurrentCommandId(true),
-					HEAP_INSERT_NO_LOGICAL, NULL);
+		CommandId	cid = HeapTupleHeaderGetRawCommandId(tuple->t_data);
+		TransactionId xid = HeapTupleHeaderGetXmin(tuple->t_data);
+
+		heap_insert(NewHeap, copiedTuple, xid, cid, HEAP_INSERT_NO_LOGICAL, NULL);
 	}
 
 	heap_freetuple(copiedTuple);
diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 5670f2bfbde..e913594fc07 100644
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -126,6 +126,18 @@ static FullTransactionId XactTopFullTransactionId = {InvalidTransactionId};
 static int	nParallelCurrentXids = 0;
 static TransactionId *ParallelCurrentXids;
 
+/*
+ * Another case that requires TransactionIdIsCurrentTransactionId() to behave
+ * specially is when REPACK CONCURRENTLY is processing data changes made in
+ * the old storage of a table by other transactions. When applying the changes
+ * to the new storage, the backend executing the CLUSTER command needs to act
+ * on behalf on those other transactions. The transactions responsible for the
+ * changes in the old storage are stored in this array, sorted by
+ * xidComparator.
+ */
+static int	nRepackCurrentXids = 0;
+static TransactionId *RepackCurrentXids = NULL;
+
 /*
  * Miscellaneous flag bits to record events which occur on the top level
  * transaction. These flags are only persisted in MyXactFlags and are intended
@@ -973,6 +985,8 @@ TransactionIdIsCurrentTransactionId(TransactionId xid)
 		int			low,
 					high;
 
+		Assert(nRepackCurrentXids == 0);
+
 		low = 0;
 		high = nParallelCurrentXids - 1;
 		while (low <= high)
@@ -992,6 +1006,21 @@ TransactionIdIsCurrentTransactionId(TransactionId xid)
 		return false;
 	}
 
+	/*
+	 * When executing CLUSTER CONCURRENTLY, the array of current transactions
+	 * is given.
+	 */
+	if (nRepackCurrentXids > 0)
+	{
+		Assert(nParallelCurrentXids == 0);
+
+		return bsearch(&xid,
+					   RepackCurrentXids,
+					   nRepackCurrentXids,
+					   sizeof(TransactionId),
+					   xidComparator) != NULL;
+	}
+
 	/*
 	 * We will return true for the Xid of the current subtransaction, any of
 	 * its subcommitted children, any of its parents, or any of their
@@ -5661,6 +5690,29 @@ EndParallelWorkerTransaction(void)
 	CurrentTransactionState->blockState = TBLOCK_DEFAULT;
 }
 
+/*
+ * SetRepackCurrentXids
+ *		Set the XID array that TransactionIdIsCurrentTransactionId() should
+ *		use.
+ */
+void
+SetRepackCurrentXids(TransactionId *xip, int xcnt)
+{
+	RepackCurrentXids = xip;
+	nRepackCurrentXids = xcnt;
+}
+
+/*
+ * ResetRepackCurrentXids
+ *		Undo the effect of SetRepackCurrentXids().
+ */
+void
+ResetRepackCurrentXids(void)
+{
+	RepackCurrentXids = NULL;
+	nRepackCurrentXids = 0;
+}
+
 /*
  * ShowTransactionState
  *		Debug support
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index 511b2bb6c43..a44724f3757 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -82,6 +82,11 @@ typedef struct
  * The following definitions are used for concurrent processing.
  */
 
+/*
+ * OID of the table being repacked by this backend.
+ */
+static Oid	repacked_rel = InvalidOid;
+
 /*
  * The locators are used to avoid logical decoding of data that we do not need
  * for our table.
@@ -125,8 +130,10 @@ static List *get_tables_to_repack_partitioned(RepackCommand cmd,
 static bool cluster_is_permitted_for_relation(RepackCommand cmd,
 											  Oid relid, Oid userid);
 
-static void begin_concurrent_repack(Relation rel);
-static void end_concurrent_repack(void);
+static void begin_concurrent_repack(Relation rel, Relation *index_p,
+									bool *entered_p);
+static void end_concurrent_repack(bool error);
+static void cluster_before_shmem_exit_callback(int code, Datum arg);
 static LogicalDecodingContext *setup_logical_decoding(Oid relid,
 													  const char *slotname,
 													  TupleDesc tupdesc);
@@ -146,6 +153,7 @@ static void apply_concurrent_delete(Relation rel, HeapTuple tup_target,
 									ConcurrentChange *change);
 static HeapTuple find_target_tuple(Relation rel, ScanKey key, int nkeys,
 								   HeapTuple tup_key,
+								   Snapshot snapshot,
 								   IndexInsertState *iistate,
 								   TupleTableSlot *ident_slot,
 								   IndexScanDesc *scan_p);
@@ -450,6 +458,8 @@ cluster_rel(RepackCommand cmd, bool usingindex,
 	bool		verbose = ((params->options & CLUOPT_VERBOSE) != 0);
 	bool		recheck = ((params->options & CLUOPT_RECHECK) != 0);
 	bool		concurrent = ((params->options & CLUOPT_CONCURRENT) != 0);
+	bool		entered,
+				success;
 
 	/*
 	 * Check that the correct lock is held. The lock mode is
@@ -620,23 +630,30 @@ cluster_rel(RepackCommand cmd, bool usingindex,
 		TransferPredicateLocksToHeapRelation(OldHeap);
 
 	/* rebuild_relation does all the dirty work */
+	entered = false;
+	success = false;
 	PG_TRY();
 	{
 		/*
-		 * For concurrent processing, make sure that our logical decoding
-		 * ignores data changes of other tables than the one we are
-		 * processing.
+		 * For concurrent processing, make sure that
+		 *
+		 * 1) our logical decoding ignores data changes of other tables than
+		 * the one we are processing.
+		 *
+		 * 2) other transactions treat this table as if it was a system / user
+		 * catalog, and WAL the relevant additional information.
 		 */
 		if (concurrent)
-			begin_concurrent_repack(OldHeap);
+			begin_concurrent_repack(OldHeap, &index, &entered);
 
 		rebuild_relation(cmd, usingindex, OldHeap, index, save_userid,
 						 verbose, concurrent);
+		success = true;
 	}
 	PG_FINALLY();
 	{
-		if (concurrent)
-			end_concurrent_repack();
+		if (concurrent && entered)
+			end_concurrent_repack(!success);
 	}
 	PG_END_TRY();
 
@@ -2396,6 +2413,47 @@ determine_clustered_index(Relation rel, bool usingindex, const char *indexname)
 }
 
 
+/*
+ * Each relation being processed by REPACK CONCURRENTLY must be in the
+ * repackedRels hashtable.
+ */
+typedef struct RepackedRel
+{
+	Oid			relid;
+	Oid			dbid;
+} RepackedRel;
+
+static HTAB *RepackedRelsHash = NULL;
+
+/*
+ * Maximum number of entries in the hashtable.
+ *
+ * A replication slot is needed for the processing, so use this GUC to
+ * allocate memory for the hashtable.
+ */
+#define	MAX_REPACKED_RELS	(max_replication_slots)
+
+Size
+RepackShmemSize(void)
+{
+	return hash_estimate_size(MAX_REPACKED_RELS, sizeof(RepackedRel));
+}
+
+void
+RepackShmemInit(void)
+{
+	HASHCTL		info;
+
+	info.keysize = sizeof(RepackedRel);
+	info.entrysize = info.keysize;
+
+	RepackedRelsHash = ShmemInitHash("Repacked Relations",
+									 MAX_REPACKED_RELS,
+									 MAX_REPACKED_RELS,
+									 &info,
+									 HASH_ELEM | HASH_BLOBS);
+}
+
 /*
  * Call this function before REPACK CONCURRENTLY starts to setup logical
  * decoding. It makes sure that other users of the table put enough
@@ -2410,11 +2468,119 @@ determine_clustered_index(Relation rel, bool usingindex, const char *indexname)
  *
  * Note that TOAST table needs no attention here as it's not scanned using
  * historic snapshot.
+ *
+ * 'index_p' is in/out argument because the function unlocks the index
+ * temporarily.
+ *
+ * 'enter_p' receives a bool value telling whether relation OID was entered
+ * into RepackedRelsHash or not.
  */
 static void
-begin_concurrent_repack(Relation rel)
+begin_concurrent_repack(Relation rel, Relation *index_p, bool *entered_p)
 {
-	Oid			toastrelid;
+	Oid			relid,
+				toastrelid;
+	Relation	index = NULL;
+	Oid			indexid = InvalidOid;
+	RepackedRel key,
+			   *entry;
+	bool		found;
+	static bool before_shmem_exit_callback_setup = false;
+
+	relid = RelationGetRelid(rel);
+	index = index_p ? *index_p : NULL;
+
+	/*
+	 * Make sure that we do not leave an entry in RepackedRelsHash if exiting
+	 * due to FATAL.
+	 */
+	if (!before_shmem_exit_callback_setup)
+	{
+		before_shmem_exit(cluster_before_shmem_exit_callback, 0);
+		before_shmem_exit_callback_setup = true;
+	}
+
+	memset(&key, 0, sizeof(key));
+	key.relid = relid;
+	key.dbid = MyDatabaseId;
+
+	*entered_p = false;
+	LWLockAcquire(RepackedRelsLock, LW_EXCLUSIVE);
+	entry = (RepackedRel *)
+		hash_search(RepackedRelsHash, &key, HASH_ENTER_NULL, &found);
+	if (found)
+	{
+		/*
+		 * Since REPACK CONCURRENTLY takes ShareRowExclusiveLock, a conflict
+		 * should occur much earlier. However that lock may be released
+		 * temporarily, see below.  Anyway, we should complain whatever the
+		 * reason of the conflict might be.
+		 */
+		ereport(ERROR,
+				(errmsg("relation \"%s\" is already being processed by REPACK CONCURRENTLY",
+						RelationGetRelationName(rel))));
+	}
+	if (entry == NULL)
+		ereport(ERROR,
+				(errmsg("too many requests for REPACK CONCURRENTLY at a time")),
+				(errhint("Please consider increasing the \"max_replication_slots\" configuration parameter.")));
+
+	/*
+	 * Even if anything fails below, the caller has to do cleanup in the
+	 * shared memory.
+	 */
+	*entered_p = true;
+
+	/*
+	 * Enable the callback to remove the entry in case of exit. We should not
+	 * do this earlier, otherwise an attempt to insert already existing entry
+	 * could make us remove that entry (inserted by another backend) during
+	 * ERROR handling.
+	 */
+	Assert(!OidIsValid(repacked_rel));
+	repacked_rel = relid;
+
+	LWLockRelease(RepackedRelsLock);
+
+	/*
+	 * Make sure that other backends are aware of the new hash entry as soon
+	 * as they open our table.
+	 */
+	CacheInvalidateRelcacheImmediate(relid);
+
+	/*
+	 * Also make sure that the existing users of the table update their
+	 * relcache entry as soon as they try to run DML commands on it.
+	 *
+	 * ShareLock is the weakest lock that conflicts with DMLs. If any backend
+	 * has a lower lock, we assume it'll accept our invalidation message when
+	 * it changes the lock mode.
+	 *
+	 * Before upgrading the lock on the relation, close the index temporarily
+	 * to avoid a deadlock if another backend running DML already has its lock
+	 * (ShareLock) on the table and waits for the lock on the index.
+	 */
+	if (index)
+	{
+		indexid = RelationGetRelid(index);
+		index_close(index, ShareUpdateExclusiveLock);
+	}
+	LockRelationOid(relid, ShareLock);
+	UnlockRelationOid(relid, ShareLock);
+	if (OidIsValid(indexid))
+	{
+		/*
+		 * Re-open the index and check that it hasn't changed while unlocked.
+		 */
+		check_index_is_clusterable(rel, indexid, ShareUpdateExclusiveLock);
+
+		/*
+		 * Return the new relcache entry to the caller. (It's been locked by
+		 * the call above.)
+		 */
+		index = index_open(indexid, NoLock);
+		*index_p = index;
+	}
 
 	/* Avoid logical decoding of other relations by this backend. */
 	repacked_rel_locator = rel->rd_locator;
@@ -2432,15 +2598,122 @@ begin_concurrent_repack(Relation rel)
 
 /*
  * Call this when done with REPACK CONCURRENTLY.
+ *
+ * 'error' tells whether the function is being called in order to handle
+ * error.
  */
 static void
-end_concurrent_repack(void)
+end_concurrent_repack(bool error)
 {
+	RepackedRel key;
+	RepackedRel *entry = NULL;
+	Oid			relid = repacked_rel;
+
+	/* Remove the relation from the hash if we managed to insert one. */
+	if (OidIsValid(repacked_rel))
+	{
+		memset(&key, 0, sizeof(key));
+		key.relid = repacked_rel;
+		key.dbid = MyDatabaseId;
+		LWLockAcquire(RepackedRelsLock, LW_EXCLUSIVE);
+		entry = hash_search(RepackedRelsHash, &key, HASH_REMOVE, NULL);
+		LWLockRelease(RepackedRelsLock);
+
+		/*
+		 * Make others refresh their information whether they should still
+		 * treat the table as catalog from the perspective of writing WAL.
+		 *
+		 * XXX Unlike entering the entry into the hashtable, we do not bother
+		 * with locking and unlocking the table here:
+		 *
+		 * 1) On normal completion (and sometimes even on ERROR), the caller
+		 * is already holding AccessExclusiveLock on the table, so there
+		 * should be no relcache reference unaware of this change.
+		 *
+		 * 2) In the other cases, the worst scenario is that the other
+		 * backends will write unnecessary information to WAL until they close
+		 * the relation.
+		 *
+		 * Should we use ShareLock mode to fix 2) at least for the non-FATAL
+		 * errors? (Our before_shmem_exit callback is in charge of FATAL, and
+		 * that probably should not try to acquire any lock.)
+		 */
+		CacheInvalidateRelcacheImmediate(repacked_rel);
+
+		/*
+		 * By clearing this variable we also disable
+		 * cluster_before_shmem_exit_callback().
+		 */
+		repacked_rel = InvalidOid;
+	}
+
 	/*
 	 * Restore normal function of (future) logical decoding for this backend.
 	 */
 	repacked_rel_locator.relNumber = InvalidOid;
 	repacked_rel_toast_locator.relNumber = InvalidOid;
+
+	/*
+	 * On normal completion (!error), we should not really fail to remove the
+	 * entry. But if it wasn't there for any reason, raise ERROR to make sure
+	 * the transaction is aborted: if other transactions, while changing the
+	 * contents of the relation, didn't know that REPACK CONCURRENTLY was in
+	 * progress, they could have missed to WAL enough information, and thus we
+	 * could have produced an inconsistent table contents.
+	 *
+	 * On the other hand, if we are already handling an error, there's no
+	 * reason to worry about inconsistent contents of the new storage because
+	 * the transaction is going to be rolled back anyway. Furthermore, by
+	 * raising ERROR here we'd shadow the original error.
+	 */
+	if (!error)
+	{
+		char	   *relname;
+
+		if (OidIsValid(relid) && entry == NULL)
+		{
+			relname = get_rel_name(relid);
+			if (!relname)
+				ereport(ERROR,
+						(errmsg("cache lookup failed for relation %u",
+								relid)));
+
+			ereport(ERROR,
+					(errmsg("relation \"%s\" not found among repacked relations",
+							relname)));
+		}
+	}
+}
+
+/*
+ * A wrapper to call end_concurrent_repack() as a before_shmem_exit callback.
+ */
+static void
+cluster_before_shmem_exit_callback(int code, Datum arg)
+{
+	if (OidIsValid(repacked_rel))
+		end_concurrent_repack(true);
+}
+
+/*
+ * Check if relation is currently being processed by REPACK CONCURRENTLY.
+ */
+bool
+is_concurrent_repack_in_progress(Oid relid)
+{
+	RepackedRel key,
+			   *entry;
+
+	memset(&key, 0, sizeof(key));
+	key.relid = relid;
+	key.dbid = MyDatabaseId;
+
+	LWLockAcquire(RepackedRelsLock, LW_SHARED);
+	entry = (RepackedRel *)
+		hash_search(RepackedRelsHash, &key, HASH_FIND, NULL);
+	LWLockRelease(RepackedRelsLock);
+
+	return entry != NULL;
 }
 
 /*
@@ -2502,6 +2775,9 @@ setup_logical_decoding(Oid relid, const char *slotname, TupleDesc tupdesc)
 	dstate->relid = relid;
 	dstate->tstore = tuplestore_begin_heap(false, false,
 										   maintenance_work_mem);
+#ifdef USE_ASSERT_CHECKING
+	dstate->last_change_xid = InvalidTransactionId;
+#endif
 
 	dstate->tupdesc = tupdesc;
 
@@ -2649,6 +2925,7 @@ apply_concurrent_changes(RepackDecodingState *dstate, Relation rel,
 		char	   *change_raw,
 				   *src;
 		ConcurrentChange change;
+		Snapshot	snapshot;
 		bool		isnull[1];
 		Datum		values[1];
 
@@ -2717,8 +2994,30 @@ apply_concurrent_changes(RepackDecodingState *dstate, Relation rel,
 
 			/*
 			 * Find the tuple to be updated or deleted.
+			 *
+			 * As the table being REPACKed concurrently is treated like a
+			 * catalog, new CID is WAL-logged and decoded. And since we use
+			 * the same XID that the original DMLs did, the snapshot used for
+			 * the logical decoding (by now converted to a non-historic MVCC
+			 * snapshot) should see the tuples inserted previously into the
+			 * new heap and/or updated there.
 			 */
-			tup_exist = find_target_tuple(rel, key, nkeys, tup_key,
+			snapshot = change.snapshot;
+
+			/*
+			 * Set what should be considered current transaction (and
+			 * subtransactions) during visibility check.
+			 *
+			 * Note that this snapshot was created from a historic snapshot
+			 * using SnapBuildMVCCFromHistoric(), which does not touch
+			 * 'subxip'. Thus, unlike in a regular MVCC snapshot, the array
+			 * only contains the transactions whose data changes we are
+			 * applying, and its subtransactions. That's exactly what we need
+			 * to check if particular xact is a "current transaction:".
+			 */
+			SetRepackCurrentXids(snapshot->subxip, snapshot->subxcnt);
+
+			tup_exist = find_target_tuple(rel, key, nkeys, tup_key, snapshot,
 										  iistate, ident_slot, &ind_scan);
 			if (tup_exist == NULL)
 				elog(ERROR, "Failed to find target tuple");
@@ -2729,6 +3028,8 @@ apply_concurrent_changes(RepackDecodingState *dstate, Relation rel,
 			else
 				apply_concurrent_delete(rel, tup_exist, &change);
 
+			ResetRepackCurrentXids();
+
 			if (tup_old != NULL)
 			{
 				pfree(tup_old);
@@ -2741,14 +3042,14 @@ apply_concurrent_changes(RepackDecodingState *dstate, Relation rel,
 		else
 			elog(ERROR, "Unrecognized kind of change: %d", change.kind);
 
-		/*
-		 * If a change was applied now, increment CID for next writes and
-		 * update the snapshot so it sees the changes we've applied so far.
-		 */
-		if (change.kind != CHANGE_UPDATE_OLD)
+		/* Free the snapshot if this is the last change that needed it. */
+		Assert(change.snapshot->active_count > 0);
+		change.snapshot->active_count--;
+		if (change.snapshot->active_count == 0)
 		{
-			CommandCounterIncrement();
-			UpdateActiveSnapshotCommandId();
+			if (change.snapshot == dstate->snapshot)
+				dstate->snapshot = NULL;
+			FreeSnapshot(change.snapshot);
 		}
 
 		/* TTSOpsMinimalTuple has .get_heap_tuple==NULL. */
@@ -2768,16 +3069,35 @@ static void
 apply_concurrent_insert(Relation rel, ConcurrentChange *change, HeapTuple tup,
 						IndexInsertState *iistate, TupleTableSlot *index_slot)
 {
+	Snapshot	snapshot = change->snapshot;
 	List	   *recheck;
 
+	/*
+	 * For INSERT, the visibility information is not important, but we use the
+	 * snapshot to get CID. Index functions might need the whole snapshot
+	 * anyway.
+	 */
+	SetRepackCurrentXids(snapshot->subxip, snapshot->subxcnt);
+
+	/*
+	 * Write the tuple into the new heap.
+	 *
+	 * The snapshot is the one we used to decode the insert (though converted
+	 * to "non-historic" MVCC snapshot), i.e. the snapshot's curcid is the
+	 * tuple CID incremented by one (due to the "new CID" WAL record that got
+	 * written along with the INSERT record). Thus if we want to use the
+	 * original CID, we need to subtract 1 from curcid.
+	 */
+	Assert(snapshot->curcid != InvalidCommandId &&
+		   snapshot->curcid > FirstCommandId);
 
 	/*
 	 * Like simple_heap_insert(), but make sure that the INSERT is not
 	 * logically decoded - see reform_and_rewrite_tuple() for more
 	 * information.
 	 */
-	heap_insert(rel, tup, GetCurrentCommandId(true), HEAP_INSERT_NO_LOGICAL,
-				NULL);
+	heap_insert(rel, tup, change->xid, snapshot->curcid - 1,
+				HEAP_INSERT_NO_LOGICAL, NULL);
 
 	/*
 	 * Update indexes.
@@ -2785,6 +3105,7 @@ apply_concurrent_insert(Relation rel, ConcurrentChange *change, HeapTuple tup,
 	 * In case functions in the index need the active snapshot and caller
 	 * hasn't set one.
 	 */
+	PushActiveSnapshot(snapshot);
 	ExecStoreHeapTuple(tup, index_slot, false);
 	recheck = ExecInsertIndexTuples(iistate->rri,
 									index_slot,
@@ -2795,6 +3116,8 @@ apply_concurrent_insert(Relation rel, ConcurrentChange *change, HeapTuple tup,
 									NIL,	/* arbiterIndexes */
 									false	/* onlySummarizing */
 		);
+	PopActiveSnapshot();
+	ResetRepackCurrentXids();
 
 	/*
 	 * If recheck is required, it must have been preformed on the source
@@ -2816,6 +3139,7 @@ apply_concurrent_update(Relation rel, HeapTuple tup, HeapTuple tup_target,
 	TU_UpdateIndexes update_indexes;
 	TM_Result	res;
 	List	   *recheck;
+	Snapshot	snapshot = change->snapshot;
 
 	/*
 	 * Write the new tuple into the new heap. ('tup' gets the TID assigned
@@ -2823,13 +3147,19 @@ apply_concurrent_update(Relation rel, HeapTuple tup, HeapTuple tup_target,
 	 *
 	 * Do it like in simple_heap_update(), except for 'wal_logical' (and
 	 * except for 'wait').
+	 *
+	 * Regarding CID, see the comment in apply_concurrent_insert().
 	 */
+	Assert(snapshot->curcid != InvalidCommandId &&
+		   snapshot->curcid > FirstCommandId);
+
 	res = heap_update(rel, &tup_target->t_self, tup,
-					  GetCurrentCommandId(true),
+					  change->xid, snapshot->curcid - 1,
 					  InvalidSnapshot,
 					  false,	/* no wait - only we are doing changes */
 					  &tmfd, &lockmode, &update_indexes,
-					  false /* wal_logical */ );
+	/* wal_logical */
+					  false);
 	if (res != TM_Ok)
 		ereport(ERROR, (errmsg("failed to apply concurrent UPDATE")));
 
@@ -2837,6 +3167,7 @@ apply_concurrent_update(Relation rel, HeapTuple tup, HeapTuple tup_target,
 
 	if (update_indexes != TU_None)
 	{
+		PushActiveSnapshot(snapshot);
 		recheck = ExecInsertIndexTuples(iistate->rri,
 										index_slot,
 										iistate->estate,
@@ -2846,6 +3177,7 @@ apply_concurrent_update(Relation rel, HeapTuple tup, HeapTuple tup_target,
 										NIL,	/* arbiterIndexes */
 		/* onlySummarizing */
 										update_indexes == TU_Summarizing);
+		PopActiveSnapshot();
 		list_free(recheck);
 	}
 
@@ -2858,6 +3190,12 @@ apply_concurrent_delete(Relation rel, HeapTuple tup_target,
 {
 	TM_Result	res;
 	TM_FailureData tmfd;
+	Snapshot	snapshot = change->snapshot;
+
+
+	/* Regarding CID, see the comment in apply_concurrent_insert(). */
+	Assert(snapshot->curcid != InvalidCommandId &&
+		   snapshot->curcid > FirstCommandId);
 
 	/*
 	 * Delete tuple from the new heap.
@@ -2865,11 +3203,11 @@ apply_concurrent_delete(Relation rel, HeapTuple tup_target,
 	 * Do it like in simple_heap_delete(), except for 'wal_logical' (and
 	 * except for 'wait').
 	 */
-	res = heap_delete(rel, &tup_target->t_self, GetCurrentCommandId(true),
-					  InvalidSnapshot, false,
-					  &tmfd,
-					  false,	/* no wait - only we are doing changes */
-					  false /* wal_logical */ );
+	res = heap_delete(rel, &tup_target->t_self, change->xid,
+					  snapshot->curcid - 1, InvalidSnapshot, false,
+					  &tmfd, false,
+	/* wal_logical */
+					  false);
 
 	if (res != TM_Ok)
 		ereport(ERROR, (errmsg("failed to apply concurrent DELETE")));
@@ -2890,7 +3228,7 @@ apply_concurrent_delete(Relation rel, HeapTuple tup_target,
  */
 static HeapTuple
 find_target_tuple(Relation rel, ScanKey key, int nkeys, HeapTuple tup_key,
-				  IndexInsertState *iistate,
+				  Snapshot snapshot, IndexInsertState *iistate,
 				  TupleTableSlot *ident_slot, IndexScanDesc *scan_p)
 {
 	IndexScanDesc scan;
@@ -2899,7 +3237,7 @@ find_target_tuple(Relation rel, ScanKey key, int nkeys, HeapTuple tup_key,
 	HeapTuple	result = NULL;
 
 	/* XXX no instrumentation for now */
-	scan = index_beginscan(rel, iistate->ident_index, GetActiveSnapshot(),
+	scan = index_beginscan(rel, iistate->ident_index, snapshot,
 						   NULL, nkeys, 0);
 	*scan_p = scan;
 	index_rescan(scan, key, nkeys, NULL, 0);
@@ -2971,6 +3309,8 @@ process_concurrent_changes(LogicalDecodingContext *ctx, XLogRecPtr end_of_wal,
 	}
 	PG_FINALLY();
 	{
+		ResetRepackCurrentXids();
+
 		if (rel_src)
 			rel_dst->rd_toastoid = InvalidOid;
 	}
diff --git a/src/backend/replication/logical/decode.c b/src/backend/replication/logical/decode.c
index 5dc4ae58ffe..9fefcffd8b3 100644
--- a/src/backend/replication/logical/decode.c
+++ b/src/backend/replication/logical/decode.c
@@ -475,9 +475,14 @@ heap_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 
 	/*
 	 * If the change is not intended for logical decoding, do not even
-	 * establish transaction for it - REPACK CONCURRENTLY is the typical use
-	 * case.
-	 *
+	 * establish transaction for it. This is particularly important if the
+	 * record was generated by REPACK CONCURRENTLY because this command uses
+	 * the original XID when doing changes in the new storage. The decoding
+	 * system probably does not expect to see the same transaction multiple
+	 * times.
+	 */
+
+	/*
 	 * First, check if REPACK CONCURRENTLY is being performed by this backend.
 	 * If so, only decode data changes of the table that it is processing, and
 	 * the changes of its TOAST relation.
@@ -504,11 +509,11 @@ heap_decode(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	 * Second, skip records which do not contain sufficient information for
 	 * the decoding.
 	 *
-	 * The problem we solve here is that REPACK CONCURRENTLY generates WAL
-	 * when doing changes in the new table. Those changes should not be useful
-	 * for any other user (such as logical replication subscription) because
-	 * the new table will eventually be dropped (after REPACK CONCURRENTLY has
-	 * assigned its file to the "old table").
+	 * One particular problem we solve here is that REPACK CONCURRENTLY
+	 * generates WAL when doing changes in the new table. Those changes should
+	 * not be decoded because reorderbuffer.c considers their XID already
+	 * committed. (REPACK CONCURRENTLY deliberately generates WAL records in
+	 * such a way that they are skipped here.)
 	 */
 	switch (info)
 	{
@@ -995,13 +1000,6 @@ DecodeInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 
 	xlrec = (xl_heap_insert *) XLogRecGetData(r);
 
-	/*
-	 * Ignore insert records without new tuples (this does happen when
-	 * raw_heap_insert marks the TOAST record as HEAP_INSERT_NO_LOGICAL).
-	 */
-	if (!(xlrec->flags & XLH_INSERT_CONTAINS_NEW_TUPLE))
-		return;
-
 	/* only interested in our database */
 	XLogRecGetBlockTag(r, 0, &target_locator, NULL, NULL);
 	if (target_locator.dbOid != ctx->slot->data.database)
diff --git a/src/backend/replication/logical/snapbuild.c b/src/backend/replication/logical/snapbuild.c
index 8e5116a9cab..72a38074a7b 100644
--- a/src/backend/replication/logical/snapbuild.c
+++ b/src/backend/replication/logical/snapbuild.c
@@ -155,7 +155,7 @@ static bool ExportInProgress = false;
 static void SnapBuildPurgeOlderTxn(SnapBuild *builder);
 
 /* snapshot building/manipulation/distribution functions */
-static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder);
+static Snapshot SnapBuildBuildSnapshot(SnapBuild *builder, XLogRecPtr lsn);
 
 static void SnapBuildFreeSnapshot(Snapshot snap);
 
@@ -352,12 +352,17 @@ SnapBuildSnapDecRefcount(Snapshot snap)
  * Build a new snapshot, based on currently committed catalog-modifying
  * transactions.
  *
+ * 'lsn' is the location of the commit record (of a catalog-changing
+ * transaction) that triggered creation of the snapshot. Pass
+ * InvalidXLogRecPtr for the transaction base snapshot or if it the user of
+ * the snapshot should not need the LSN.
+ *
  * In-progress transactions with catalog access are *not* allowed to modify
  * these snapshots; they have to copy them and fill in appropriate ->curcid
  * and ->subxip/subxcnt values.
  */
 static Snapshot
-SnapBuildBuildSnapshot(SnapBuild *builder)
+SnapBuildBuildSnapshot(SnapBuild *builder, XLogRecPtr lsn)
 {
 	Snapshot	snapshot;
 	Size		ssize;
@@ -425,6 +430,7 @@ SnapBuildBuildSnapshot(SnapBuild *builder)
 	snapshot->active_count = 0;
 	snapshot->regd_count = 0;
 	snapshot->snapXactCompletionCount = 0;
+	snapshot->lsn = lsn;
 
 	return snapshot;
 }
@@ -461,7 +467,7 @@ SnapBuildInitialSnapshot(SnapBuild *builder)
 	if (TransactionIdIsValid(MyProc->xmin))
 		elog(ERROR, "cannot build an initial slot snapshot when MyProc->xmin already is valid");
 
-	snap = SnapBuildBuildSnapshot(builder);
+	snap = SnapBuildBuildSnapshot(builder, InvalidXLogRecPtr);
 
 	/*
 	 * We know that snap->xmin is alive, enforced by the logical xmin
@@ -502,7 +508,7 @@ SnapBuildInitialSnapshotForRepack(SnapBuild *builder)
 
 	Assert(builder->state == SNAPBUILD_CONSISTENT);
 
-	snap = SnapBuildBuildSnapshot(builder);
+	snap = SnapBuildBuildSnapshot(builder, InvalidXLogRecPtr);
 	return SnapBuildMVCCFromHistoric(snap, false);
 }
 
@@ -636,7 +642,7 @@ SnapBuildGetOrBuildSnapshot(SnapBuild *builder)
 	/* only build a new snapshot if we don't have a prebuilt one */
 	if (builder->snapshot == NULL)
 	{
-		builder->snapshot = SnapBuildBuildSnapshot(builder);
+		builder->snapshot = SnapBuildBuildSnapshot(builder, InvalidXLogRecPtr);
 		/* increase refcount for the snapshot builder */
 		SnapBuildSnapIncRefcount(builder->snapshot);
 	}
@@ -716,7 +722,7 @@ SnapBuildProcessChange(SnapBuild *builder, TransactionId xid, XLogRecPtr lsn)
 		/* only build a new snapshot if we don't have a prebuilt one */
 		if (builder->snapshot == NULL)
 		{
-			builder->snapshot = SnapBuildBuildSnapshot(builder);
+			builder->snapshot = SnapBuildBuildSnapshot(builder, lsn);
 			/* increase refcount for the snapshot builder */
 			SnapBuildSnapIncRefcount(builder->snapshot);
 		}
@@ -1130,7 +1136,7 @@ SnapBuildCommitTxn(SnapBuild *builder, XLogRecPtr lsn, TransactionId xid,
 		if (builder->snapshot)
 			SnapBuildSnapDecRefcount(builder->snapshot);
 
-		builder->snapshot = SnapBuildBuildSnapshot(builder);
+		builder->snapshot = SnapBuildBuildSnapshot(builder, lsn);
 
 		/* we might need to execute invalidations, add snapshot */
 		if (!ReorderBufferXidHasBaseSnapshot(builder->reorder, xid))
@@ -1958,7 +1964,7 @@ SnapBuildRestore(SnapBuild *builder, XLogRecPtr lsn)
 	{
 		SnapBuildSnapDecRefcount(builder->snapshot);
 	}
-	builder->snapshot = SnapBuildBuildSnapshot(builder);
+	builder->snapshot = SnapBuildBuildSnapshot(builder, InvalidXLogRecPtr);
 	SnapBuildSnapIncRefcount(builder->snapshot);
 
 	ReorderBufferSetRestartPoint(builder->reorder, lsn);
diff --git a/src/backend/replication/pgoutput_repack/pgoutput_repack.c b/src/backend/replication/pgoutput_repack/pgoutput_repack.c
index 687fbbc59bb..28bd16f9cc7 100644
--- a/src/backend/replication/pgoutput_repack/pgoutput_repack.c
+++ b/src/backend/replication/pgoutput_repack/pgoutput_repack.c
@@ -32,7 +32,8 @@ static void plugin_truncate(struct LogicalDecodingContext *ctx,
 							Relation relations[],
 							ReorderBufferChange *change);
 static void store_change(LogicalDecodingContext *ctx,
-						 ConcurrentChangeKind kind, HeapTuple tuple);
+						 ConcurrentChangeKind kind, HeapTuple tuple,
+						 TransactionId xid);
 
 void
 _PG_output_plugin_init(OutputPluginCallbacks *cb)
@@ -100,6 +101,7 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 			  Relation relation, ReorderBufferChange *change)
 {
 	RepackDecodingState *dstate;
+	Snapshot	snapshot;
 
 	dstate = (RepackDecodingState *) ctx->output_writer_private;
 
@@ -107,6 +109,48 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 	if (relation->rd_id != dstate->relid)
 		return;
 
+	/*
+	 * Catalog snapshot is fine because the table we are processing is
+	 * temporarily considered a user catalog table.
+	 */
+	snapshot = GetCatalogSnapshot(InvalidOid);
+	Assert(snapshot->snapshot_type == SNAPSHOT_HISTORIC_MVCC);
+	Assert(!snapshot->suboverflowed);
+
+	/*
+	 * This should not happen, but if we don't have enough information to
+	 * apply a new snapshot, the consequences would be bad. Thus prefer ERROR
+	 * to Assert().
+	 */
+	if (XLogRecPtrIsInvalid(snapshot->lsn))
+		ereport(ERROR, (errmsg("snapshot has invalid LSN")));
+
+	/*
+	 * reorderbuffer.c changes the catalog snapshot as soon as it sees a new
+	 * CID or a commit record of a catalog-changing transaction.
+	 */
+	if (dstate->snapshot == NULL || snapshot->lsn != dstate->snapshot_lsn ||
+		snapshot->curcid != dstate->snapshot->curcid)
+	{
+		/* CID should not go backwards. */
+		Assert(dstate->snapshot == NULL ||
+			   snapshot->curcid >= dstate->snapshot->curcid ||
+			   change->txn->xid != dstate->last_change_xid);
+
+		/*
+		 * XXX Is it a problem that the copy is created in
+		 * TopTransactionContext?
+		 *
+		 * XXX Wouldn't it be o.k. for SnapBuildMVCCFromHistoric() to set xcnt
+		 * to 0 instead of converting xip in this case? The point is that
+		 * transactions which are still in progress from the perspective of
+		 * reorderbuffer.c could not be replayed yet, so we do not need to
+		 * examine their XIDs.
+		 */
+		dstate->snapshot = SnapBuildMVCCFromHistoric(snapshot, false);
+		dstate->snapshot_lsn = snapshot->lsn;
+	}
+
 	/* Decode entry depending on its type */
 	switch (change->action)
 	{
@@ -124,7 +168,7 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 				if (newtuple == NULL)
 					elog(ERROR, "Incomplete insert info.");
 
-				store_change(ctx, CHANGE_INSERT, newtuple);
+				store_change(ctx, CHANGE_INSERT, newtuple, change->txn->xid);
 			}
 			break;
 		case REORDER_BUFFER_CHANGE_UPDATE:
@@ -141,9 +185,11 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 					elog(ERROR, "Incomplete update info.");
 
 				if (oldtuple != NULL)
-					store_change(ctx, CHANGE_UPDATE_OLD, oldtuple);
+					store_change(ctx, CHANGE_UPDATE_OLD, oldtuple,
+								 change->txn->xid);
 
-				store_change(ctx, CHANGE_UPDATE_NEW, newtuple);
+				store_change(ctx, CHANGE_UPDATE_NEW, newtuple,
+							 change->txn->xid);
 			}
 			break;
 		case REORDER_BUFFER_CHANGE_DELETE:
@@ -156,7 +202,7 @@ plugin_change(LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 				if (oldtuple == NULL)
 					elog(ERROR, "Incomplete delete info.");
 
-				store_change(ctx, CHANGE_DELETE, oldtuple);
+				store_change(ctx, CHANGE_DELETE, oldtuple, change->txn->xid);
 			}
 			break;
 		default:
@@ -190,13 +236,13 @@ plugin_truncate(struct LogicalDecodingContext *ctx, ReorderBufferTXN *txn,
 	if (i == nrelations)
 		return;
 
-	store_change(ctx, CHANGE_TRUNCATE, NULL);
+	store_change(ctx, CHANGE_TRUNCATE, NULL, InvalidTransactionId);
 }
 
 /* Store concurrent data change. */
 static void
 store_change(LogicalDecodingContext *ctx, ConcurrentChangeKind kind,
-			 HeapTuple tuple)
+			 HeapTuple tuple, TransactionId xid)
 {
 	RepackDecodingState *dstate;
 	char	   *change_raw;
@@ -266,6 +312,11 @@ store_change(LogicalDecodingContext *ctx, ConcurrentChangeKind kind,
 	dst = dst_start + SizeOfConcurrentChange;
 	memcpy(dst, tuple->t_data, tuple->t_len);
 
+	/* Initialize the other fields. */
+	change.xid = xid;
+	change.snapshot = dstate->snapshot;
+	dstate->snapshot->active_count++;
+
 	/* The data has been copied. */
 	if (flattened)
 		pfree(tuple);
@@ -279,6 +330,9 @@ store:
 	isnull[0] = false;
 	tuplestore_putvalues(dstate->tstore, dstate->tupdesc_change,
 						 values, isnull);
+#ifdef USE_ASSERT_CHECKING
+	dstate->last_change_xid = xid;
+#endif
 
 	/* Accounting. */
 	dstate->nchanges++;
diff --git a/src/backend/storage/ipc/ipci.c b/src/backend/storage/ipc/ipci.c
index e9ddf39500c..e24e1795aa9 100644
--- a/src/backend/storage/ipc/ipci.c
+++ b/src/backend/storage/ipc/ipci.c
@@ -151,6 +151,7 @@ CalculateShmemSize(int *num_semaphores)
 	size = add_size(size, InjectionPointShmemSize());
 	size = add_size(size, SlotSyncShmemSize());
 	size = add_size(size, AioShmemSize());
+	size = add_size(size, RepackShmemSize());
 
 	/* include additional requested shmem from preload libraries */
 	size = add_size(size, total_addin_request);
@@ -344,6 +345,7 @@ CreateOrAttachShmemStructs(void)
 	WaitEventCustomShmemInit();
 	InjectionPointShmemInit();
 	AioShmemInit();
+	RepackShmemInit();
 }
 
 /*
diff --git a/src/backend/utils/activity/wait_event_names.txt b/src/backend/utils/activity/wait_event_names.txt
index 5427da5bc1b..e94c83726d6 100644
--- a/src/backend/utils/activity/wait_event_names.txt
+++ b/src/backend/utils/activity/wait_event_names.txt
@@ -352,6 +352,7 @@ DSMRegistry	"Waiting to read or update the dynamic shared memory registry."
 InjectionPoint	"Waiting to read or update information related to injection points."
 SerialControl	"Waiting to read or update shared <filename>pg_serial</filename> state."
 AioWorkerSubmissionQueue	"Waiting to access AIO worker submission queue."
+RepackedRels	"Waiting to access to hash table with list of repacked relations."
 
 #
 # END OF PREDEFINED LWLOCKS (DO NOT CHANGE THIS LINE)
diff --git a/src/backend/utils/cache/inval.c b/src/backend/utils/cache/inval.c
index 02505c88b8e..ecaa2283c2a 100644
--- a/src/backend/utils/cache/inval.c
+++ b/src/backend/utils/cache/inval.c
@@ -1643,6 +1643,27 @@ CacheInvalidateRelcache(Relation relation)
 								 databaseId, relationId);
 }
 
+/*
+ * CacheInvalidateRelcacheImmediate
+ *		Send invalidation message for the specified relation's relcache entry.
+ *
+ * Currently this is used in REPACK CONCURRENTLY, to make sure that other
+ * backends are aware that the command is being executed for the relation.
+ */
+void
+CacheInvalidateRelcacheImmediate(Oid relid)
+{
+	SharedInvalidationMessage msg;
+
+	msg.rc.id = SHAREDINVALRELCACHE_ID;
+	msg.rc.dbId = MyDatabaseId;
+	msg.rc.relId = relid;
+	/* check AddCatcacheInvalidationMessage() for an explanation */
+	VALGRIND_MAKE_MEM_DEFINED(&msg, sizeof(msg));
+
+	SendSharedInvalidMessages(&msg, 1);
+}
+
 /*
  * CacheInvalidateRelcacheAll
  *		Register invalidation of the whole relcache at the end of command.
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index d27a4c30548..ea565b5b053 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -1279,6 +1279,10 @@ retry:
 	/* make sure relation is marked as having no open file yet */
 	relation->rd_smgr = NULL;
 
+	/* Is REPACK CONCURRENTLY in progress? */
+	relation->rd_repack_concurrent =
+		is_concurrent_repack_in_progress(targetRelId);
+
 	/*
 	 * now we can free the memory allocated for pg_class_tuple
 	 */
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index b82dd17a966..981425f23b6 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -316,22 +316,24 @@ extern BulkInsertState GetBulkInsertState(void);
 extern void FreeBulkInsertState(BulkInsertState);
 extern void ReleaseBulkInsertStatePin(BulkInsertState bistate);
 
-extern void heap_insert(Relation relation, HeapTuple tup, CommandId cid,
-						int options, BulkInsertState bistate);
+extern void heap_insert(Relation relation, HeapTuple tup, TransactionId xid,
+						CommandId cid, int options, BulkInsertState bistate);
 extern void heap_multi_insert(Relation relation, struct TupleTableSlot **slots,
 							  int ntuples, CommandId cid, int options,
 							  BulkInsertState bistate);
 extern TM_Result heap_delete(Relation relation, ItemPointer tid,
-							 CommandId cid, Snapshot crosscheck, bool wait,
+							 TransactionId xid, CommandId cid,
+							 Snapshot crosscheck, bool wait,
 							 struct TM_FailureData *tmfd, bool changingPart,
 							 bool wal_logical);
 extern void heap_finish_speculative(Relation relation, ItemPointer tid);
 extern void heap_abort_speculative(Relation relation, ItemPointer tid);
 extern TM_Result heap_update(Relation relation, ItemPointer otid,
-							 HeapTuple newtup,
+							 HeapTuple newtup, TransactionId xid,
 							 CommandId cid, Snapshot crosscheck, bool wait,
 							 struct TM_FailureData *tmfd, LockTupleMode *lockmode,
-							 TU_UpdateIndexes *update_indexes, bool wal_logical);
+							 TU_UpdateIndexes *update_indexes,
+							 bool wal_logical);
 extern TM_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
 								 CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
 								 bool follow_updates,
diff --git a/src/include/access/xact.h b/src/include/access/xact.h
index b2bc10ee041..fbb66d559b6 100644
--- a/src/include/access/xact.h
+++ b/src/include/access/xact.h
@@ -482,6 +482,8 @@ extern Size EstimateTransactionStateSpace(void);
 extern void SerializeTransactionState(Size maxsize, char *start_address);
 extern void StartParallelWorkerTransaction(char *tstatespace);
 extern void EndParallelWorkerTransaction(void);
+extern void SetRepackCurrentXids(TransactionId *xip, int xcnt);
+extern void ResetRepackCurrentXids(void);
 extern bool IsTransactionBlock(void);
 extern bool IsTransactionOrTransactionBlock(void);
 extern char TransactionBlockStatusCode(void);
diff --git a/src/include/commands/cluster.h b/src/include/commands/cluster.h
index 4a508c57a50..5dba3d427f5 100644
--- a/src/include/commands/cluster.h
+++ b/src/include/commands/cluster.h
@@ -61,6 +61,14 @@ typedef struct ConcurrentChange
 	/* See the enum above. */
 	ConcurrentChangeKind kind;
 
+	/* Transaction that changes the data. */
+	TransactionId xid;
+
+	/*
+	 * Historic catalog snapshot that was used to decode this change.
+	 */
+	Snapshot	snapshot;
+
 	/*
 	 * The actual tuple.
 	 *
@@ -92,6 +100,8 @@ typedef struct RepackDecodingState
 	 * tuplestore does this transparently.
 	 */
 	Tuplestorestate *tstore;
+	/* XID of the last change added to tstore. */
+	TransactionId last_change_xid PG_USED_FOR_ASSERTS_ONLY;
 
 	/* The current number of changes in tstore. */
 	double		nchanges;
@@ -112,6 +122,14 @@ typedef struct RepackDecodingState
 	/* Slot to retrieve data from tstore. */
 	TupleTableSlot *tsslot;
 
+	/*
+	 * Historic catalog snapshot that was used to decode the most recent
+	 * change.
+	 */
+	Snapshot	snapshot;
+	/* LSN of the record  */
+	XLogRecPtr	snapshot_lsn;
+
 	ResourceOwner resowner;
 } RepackDecodingState;
 
@@ -141,4 +159,8 @@ extern void finish_heap_swap(Oid OIDOldHeap, Oid OIDNewHeap,
 							 MultiXactId cutoffMulti,
 							 char newrelpersistence);
 
+extern Size RepackShmemSize(void);
+extern void RepackShmemInit(void);
+extern bool is_concurrent_repack_in_progress(Oid relid);
+
 #endif							/* CLUSTER_H */
diff --git a/src/include/storage/lwlocklist.h b/src/include/storage/lwlocklist.h
index 06a1ffd4b08..9a9880b3073 100644
--- a/src/include/storage/lwlocklist.h
+++ b/src/include/storage/lwlocklist.h
@@ -85,6 +85,7 @@ PG_LWLOCK(50, DSMRegistry)
 PG_LWLOCK(51, InjectionPoint)
 PG_LWLOCK(52, SerialControl)
 PG_LWLOCK(53, AioWorkerSubmissionQueue)
+PG_LWLOCK(54, RepackedRels)
 
 /*
  * There also exist several built-in LWLock tranches.  As with the predefined
diff --git a/src/include/utils/inval.h b/src/include/utils/inval.h
index 9b871caef62..ae9dee394dc 100644
--- a/src/include/utils/inval.h
+++ b/src/include/utils/inval.h
@@ -50,6 +50,8 @@ extern void CacheInvalidateCatalog(Oid catalogId);
 
 extern void CacheInvalidateRelcache(Relation relation);
 
+extern void CacheInvalidateRelcacheImmediate(Oid relid);
+
 extern void CacheInvalidateRelcacheAll(void);
 
 extern void CacheInvalidateRelcacheByTuple(HeapTuple classTuple);
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index b552359915f..66de3bc0c29 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -253,6 +253,9 @@ typedef struct RelationData
 	bool		pgstat_enabled; /* should relation stats be counted */
 	/* use "struct" here to avoid needing to include pgstat.h: */
 	struct PgStat_TableStatus *pgstat_info; /* statistics collection area */
+
+	/* Is REPACK CONCURRENTLY being performed on this relation? */
+	bool		rd_repack_concurrent;
 } RelationData;
 
 
@@ -695,7 +698,9 @@ RelationCloseSmgr(Relation relation)
 #define RelationIsAccessibleInLogicalDecoding(relation) \
 	(XLogLogicalInfoActive() && \
 	 RelationNeedsWAL(relation) && \
-	 (IsCatalogRelation(relation) || RelationIsUsedAsCatalogTable(relation)))
+	 (IsCatalogRelation(relation) || \
+	  RelationIsUsedAsCatalogTable(relation) || \
+	  (relation)->rd_repack_concurrent))
 
 /*
  * RelationIsLogicallyLogged
diff --git a/src/include/utils/snapshot.h b/src/include/utils/snapshot.h
index 0e546ec1497..014f27db7d7 100644
--- a/src/include/utils/snapshot.h
+++ b/src/include/utils/snapshot.h
@@ -13,6 +13,7 @@
 #ifndef SNAPSHOT_H
 #define SNAPSHOT_H
 
+#include "access/xlogdefs.h"
 #include "lib/pairingheap.h"
 
 
@@ -201,6 +202,8 @@ typedef struct SnapshotData
 	uint32		regd_count;		/* refcount on RegisteredSnapshots */
 	pairingheap_node ph_node;	/* link in the RegisteredSnapshots heap */
 
+	XLogRecPtr	lsn;			/* position in the WAL stream when taken */
+
 	/*
 	 * The transaction completion count at the time GetSnapshotData() built
 	 * this snapshot. Allows to avoid re-computing static snapshots when no
diff --git a/src/test/modules/injection_points/specs/repack.spec b/src/test/modules/injection_points/specs/repack.spec
index 75850334986..3711a7c92b9 100644
--- a/src/test/modules/injection_points/specs/repack.spec
+++ b/src/test/modules/injection_points/specs/repack.spec
@@ -86,9 +86,6 @@ step change_new
 # When applying concurrent data changes, we should see the effects of an
 # in-progress subtransaction.
 #
-# XXX Not sure this test is useful now - it was designed for the patch that
-# preserves tuple visibility and which therefore modifies
-# TransactionIdIsCurrentTransactionId().
 step change_subxact1
 {
 	BEGIN;
@@ -103,7 +100,6 @@ step change_subxact1
 # When applying concurrent data changes, we should not see the effects of a
 # rolled back subtransaction.
 #
-# XXX Is this test useful? See above.
 step change_subxact2
 {
 	BEGIN;
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index b64ab8dfab4..9f5f331cad6 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2540,6 +2540,7 @@ ReorderBufferTupleCidKey
 ReorderBufferUpdateProgressTxnCB
 ReorderTuple
 RepOriginId
+RepackedRel
 RepackCommand
 RepackDecodingState
 RepackStmt
-- 
2.39.5


--3q6txozlgl6t37td--





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Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed)
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2020-03-19 06:11 [PATCH v49 5/7] Doc part of shared-memory based stats collector. Kyotaro Horiguchi <[email protected]>
2025-08-30 17:40 [PATCH v20 6/6] Preserve visibility information of the concurrent data changes. Álvaro Herrera <[email protected]>

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