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* [PATCH v5 1/3] Adding per backend commit and rollback counters
@ 2025-08-04 08:14 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-04 08:14 UTC (permalink / raw)
It relies on the existing per backend statistics that has been added in
9aea73fc61d. The new pending counters are updated when the database ones are
flushed (to reduce the overhead of incrementing new counters).
---
src/backend/utils/activity/pgstat_backend.c | 42 +++++++++++++++++++-
src/backend/utils/activity/pgstat_database.c | 7 ++++
src/include/pgstat.h | 15 +++++++
src/include/utils/pgstat_internal.h | 3 +-
4 files changed, 65 insertions(+), 2 deletions(-)
74.4% src/backend/utils/activity/
7.8% src/include/utils/
17.7% src/include/
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 7727fed3bda..42bfb9cd38f 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -37,7 +37,7 @@
* reported within critical sections so we use static memory in order to avoid
* memory allocation.
*/
-static PgStat_BackendPending PendingBackendStats;
+PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
/*
@@ -48,6 +48,11 @@ static bool backend_has_iostats = false;
*/
static WalUsage prevBackendWalUsage;
+/*
+ * For backend commit and rollback statistics.
+ */
+bool backend_has_xactstats = false;
+
/*
* Utility routines to report I/O stats for backends, kept here to avoid
* exposing PendingBackendStats to the outside world.
@@ -261,6 +266,34 @@ pgstat_flush_backend_entry_wal(PgStat_EntryRef *entry_ref)
prevBackendWalUsage = pgWalUsage;
}
+/*
+ * Flush out locally pending backend transaction statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+
+ /*
+ * This function can be called even if nothing at all has happened for
+ * transaction statistics. In this case, avoid unnecessarily modifying
+ * the stats entry.
+ */
+ if (!backend_has_xactstats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+
+ shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
+ shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+
+ PendingBackendStats.pending_xact_commit = 0;
+ PendingBackendStats.pending_xact_rollback = 0;
+
+ backend_has_xactstats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -285,6 +318,10 @@ pgstat_flush_backend(bool nowait, uint32 flags)
pgstat_backend_wal_have_pending())
has_pending_data = true;
+ /* Some transaction data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -300,6 +337,9 @@ pgstat_flush_backend(bool nowait, uint32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_WAL)
pgstat_flush_backend_entry_wal(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_XACT)
+ pgstat_flush_backend_entry_xact(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
diff --git a/src/backend/utils/activity/pgstat_database.c b/src/backend/utils/activity/pgstat_database.c
index 933dcb5cae5..218ff5e653c 100644
--- a/src/backend/utils/activity/pgstat_database.c
+++ b/src/backend/utils/activity/pgstat_database.c
@@ -352,6 +352,13 @@ pgstat_update_dbstats(TimestampTz ts)
dbentry->blk_read_time += pgStatBlockReadTime;
dbentry->blk_write_time += pgStatBlockWriteTime;
+ /* Do the same for backend stats */
+ PendingBackendStats.pending_xact_commit += pgStatXactCommit;
+ PendingBackendStats.pending_xact_rollback += pgStatXactRollback;
+
+ backend_has_xactstats = true;
+ pgstat_report_fixed = true;
+
if (pgstat_should_report_connstat())
{
long secs;
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 8e3549c3752..5d73c4dfbcf 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -523,6 +523,8 @@ typedef struct PgStat_Backend
TimestampTz stat_reset_timestamp;
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
+ PgStat_Counter xact_commit;
+ PgStat_Counter xact_rollback;
} PgStat_Backend;
/* ---------
@@ -535,6 +537,12 @@ typedef struct PgStat_BackendPending
* Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
*/
PgStat_PendingIO pending_io;
+
+ /*
+ * Transaction statistics pending flush.
+ */
+ PgStat_Counter pending_xact_commit;
+ PgStat_Counter pending_xact_rollback;
} PgStat_BackendPending;
/*
@@ -844,6 +852,13 @@ extern PGDLLIMPORT int pgstat_track_functions;
extern PGDLLIMPORT int pgstat_fetch_consistency;
+/*
+ * Variables in pgstat_backend.c
+ */
+
+extern PGDLLIMPORT PgStat_BackendPending PendingBackendStats;
+extern PGDLLIMPORT bool backend_has_xactstats;
+
/*
* Variables in pgstat_bgwriter.c
*/
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index eed4c6b359c..8077c65e938 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -707,7 +707,8 @@ extern void pgstat_archiver_snapshot_cb(void);
/* flags for pgstat_flush_backend() */
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL)
+#define PGSTAT_BACKEND_FLUSH_XACT (1 << 2) /* Flush xact statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_XACT)
extern bool pgstat_flush_backend(bool nowait, uint32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
--
2.34.1
--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="v5-0002-Adding-XID-generation-count-per-backend.patch"
^ permalink raw reply [nested|flat] 10+ messages in thread
* [PATCH v2] Adding per backend commit and rollback counters
@ 2025-08-04 08:14 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-04 08:14 UTC (permalink / raw)
This commit adds 2 functions: pg_stat_get_backend_xact_commit() and
pg_stat_get_backend_xact_rollback() to report the number of transactions that
have been committed/rolled back for a given backend PID.
It relies on the existing per backend statistics that has been added in
9aea73fc61d.
---
doc/src/sgml/monitoring.sgml | 36 +++++++++++++
src/backend/utils/activity/pgstat_backend.c | 60 +++++++++++++++++++++
src/backend/utils/activity/pgstat_xact.c | 1 +
src/backend/utils/adt/pgstatfuncs.c | 22 ++++++++
src/include/catalog/pg_proc.dat | 9 ++++
src/include/pgstat.h | 8 +++
src/include/utils/pgstat_internal.h | 4 +-
src/test/regress/expected/stats.out | 17 ++++++
src/test/regress/sql/stats.sql | 10 ++++
9 files changed, 166 insertions(+), 1 deletion(-)
26.1% doc/src/sgml/
29.1% src/backend/utils/activity/
11.9% src/backend/utils/adt/
9.4% src/include/catalog/
3.9% src/include/utils/
3.3% src/include/
8.9% src/test/regress/expected/
7.1% src/test/regress/sql/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..77b41e02b82 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -4921,6 +4921,42 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-xact-commit" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_xact_commit</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_xact_commit</function> ( <type>integer</type> )
+ <returnvalue>bigint</returnvalue>
+ </para>
+ <para>
+ Returns the number of transactions that have been committed by the backend
+ with the specified process ID.
+ </para>
+ <para>
+ The function does not return statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry id="pg-stat-get-backend-xact-rollback" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_xact_rollback</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_xact_rollback</function> ( <type>integer</type> )
+ <returnvalue>bigint</returnvalue>
+ </para>
+ <para>
+ Returns the number of transactions that have been rolled back by the backend
+ with the specified process ID.
+ </para>
+ <para>
+ The function does not return statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 8714a85e2d9..12ae9a8d321 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -47,6 +47,11 @@ static bool backend_has_iostats = false;
*/
static WalUsage prevBackendWalUsage;
+/*
+ * For backend commit and rollback statistics.
+ */
+static bool backend_has_xactstats = false;
+
/*
* Utility routines to report I/O stats for backends, kept here to avoid
* exposing PendingBackendStats to the outside world.
@@ -259,6 +264,34 @@ pgstat_flush_backend_entry_wal(PgStat_EntryRef *entry_ref)
prevBackendWalUsage = pgWalUsage;
}
+/*
+ * Flush out locally pending backend xact statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+
+ /*
+ * This function can be called even if nothing at all has happened for
+ * XACT statistics. In this case, avoid unnecessarily modifying the stats
+ * entry.
+ */
+ if (!backend_has_xactstats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+
+ shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
+ shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+
+ PendingBackendStats.pending_xact_commit = 0;
+ PendingBackendStats.pending_xact_rollback = 0;
+
+ backend_has_xactstats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -283,6 +316,10 @@ pgstat_flush_backend(bool nowait, bits32 flags)
pgstat_backend_wal_have_pending())
has_pending_data = true;
+ /* Some XACT data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -298,6 +335,9 @@ pgstat_flush_backend(bool nowait, bits32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_WAL)
pgstat_flush_backend_entry_wal(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_XACT)
+ pgstat_flush_backend_entry_xact(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -400,3 +440,23 @@ pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header, TimestampTz ts)
{
((PgStatShared_Backend *) header)->stats.stat_reset_timestamp = ts;
}
+
+void
+AtEOXact_PgStat_Backend(bool isCommit, bool parallel)
+{
+ /* Don't count parallel worker transaction stats */
+ if (!parallel)
+ {
+ /*
+ * Count transaction commit or abort. (We use counters, not just
+ * bools, in case the reporting message isn't sent right away.)
+ */
+ if (isCommit)
+ PendingBackendStats.pending_xact_commit++;
+ else
+ PendingBackendStats.pending_xact_rollback++;
+
+ backend_has_xactstats = true;
+ pgstat_report_fixed = true;
+ }
+}
diff --git a/src/backend/utils/activity/pgstat_xact.c b/src/backend/utils/activity/pgstat_xact.c
index bc9864bd8d9..cd1c501c165 100644
--- a/src/backend/utils/activity/pgstat_xact.c
+++ b/src/backend/utils/activity/pgstat_xact.c
@@ -42,6 +42,7 @@ AtEOXact_PgStat(bool isCommit, bool parallel)
PgStat_SubXactStatus *xact_state;
AtEOXact_PgStat_Database(isCommit, parallel);
+ AtEOXact_PgStat_Backend(isCommit, parallel);
/* handle transactional stats information */
xact_state = pgStatXactStack;
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..6436129f516 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1606,6 +1606,28 @@ pg_stat_get_backend_io(PG_FUNCTION_ARGS)
return (Datum) 0;
}
+#define PG_STAT_GET_BACKENDENTRY_INT64(stat) \
+Datum \
+CppConcat(pg_stat_get_backend_,stat)(PG_FUNCTION_ARGS) \
+{ \
+ int pid; \
+ PgStat_Backend *backend_stats; \
+ \
+ pid = PG_GETARG_INT32(0); \
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);\
+ \
+ if (!backend_stats) \
+ PG_RETURN_NULL(); \
+ else \
+ PG_RETURN_INT64(backend_stats->stat); \
+}
+
+/* pg_stat_get_backend_xact_commit */
+PG_STAT_GET_BACKENDENTRY_INT64(xact_commit)
+
+/* pg_stat_get_backend_xact_rollback */
+PG_STAT_GET_BACKENDENTRY_INT64(xact_rollback)
+
/*
* pg_stat_wal_build_tuple
*
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..f5085d4e016 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6010,6 +6010,15 @@
proargnames => '{backend_pid,backend_type,object,context,reads,read_bytes,read_time,writes,write_bytes,write_time,writebacks,writeback_time,extends,extend_bytes,extend_time,hits,evictions,reuses,fsyncs,fsync_time,stats_reset}',
prosrc => 'pg_stat_get_backend_io' },
+{ oid => '8170', descr => 'statistics: backend transactions committed',
+ proname => 'pg_stat_get_backend_xact_commit', provolatile => 's',
+ proparallel => 'r', prorettype => 'int8', proargtypes => 'int4',
+ prosrc => 'pg_stat_get_backend_xact_commit' },
+{ oid => '8916', descr => 'statistics: backend transactions rolled back',
+ proname => 'pg_stat_get_backend_xact_rollback', provolatile => 's',
+ proparallel => 'r', prorettype => 'int8', proargtypes => 'int4',
+ prosrc => 'pg_stat_get_backend_xact_rollback' },
+
{ oid => '1136', descr => 'statistics: information about WAL activity',
proname => 'pg_stat_get_wal', proisstrict => 'f', provolatile => 's',
proparallel => 'r', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 202bd2d5ace..d3491faaff2 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -490,6 +490,8 @@ typedef struct PgStat_Backend
TimestampTz stat_reset_timestamp;
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
+ PgStat_Counter xact_commit;
+ PgStat_Counter xact_rollback;
} PgStat_Backend;
/* ---------
@@ -502,6 +504,12 @@ typedef struct PgStat_BackendPending
* Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
*/
PgStat_PendingIO pending_io;
+
+ /*
+ * Xact statistics pending flush.
+ */
+ PgStat_Counter pending_xact_commit;
+ PgStat_Counter pending_xact_rollback;
} PgStat_BackendPending;
/*
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index 6cf00008f63..23ea8ffd618 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -616,12 +616,14 @@ extern void pgstat_archiver_snapshot_cb(void);
/* flags for pgstat_flush_backend() */
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL)
+#define PGSTAT_BACKEND_FLUSH_XACT (1 << 2) /* Flush xact statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_XACT)
extern bool pgstat_flush_backend(bool nowait, bits32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
extern void pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header,
TimestampTz ts);
+extern void AtEOXact_PgStat_Backend(bool isCommit, bool parallel);
/*
* Functions in pgstat_bgwriter.c
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..0d316f94e40 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT pg_stat_get_backend_xact_commit AS xact_commit_before
+ FROM pg_stat_get_backend_xact_commit(pg_backend_pid()) \gset
BEGIN;
UPDATE trunc_stats_test1 SET id = id + 100;
TRUNCATE trunc_stats_test1;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush
+--------------------------
+
+(1 row)
+
+SELECT pg_stat_get_backend_xact_commit AS xact_commit_after
+ FROM pg_stat_get_backend_xact_commit(pg_backend_pid()) \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column?
+----------
+ t
+(1 row)
+
-- use a savepoint: 1 insert, 1 live
BEGIN;
INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..d629140d880 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT pg_stat_get_backend_xact_commit AS xact_commit_before
+ FROM pg_stat_get_backend_xact_commit(pg_backend_pid()) \gset
+
BEGIN;
UPDATE trunc_stats_test1 SET id = id + 100;
TRUNCATE trunc_stats_test1;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
COMMIT;
+SELECT pg_stat_force_next_flush();
+SELECT pg_stat_get_backend_xact_commit AS xact_commit_after
+ FROM pg_stat_get_backend_xact_commit(pg_backend_pid()) \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
-- use a savepoint: 1 insert, 1 live
BEGIN;
INSERT INTO trunc_stats_test2 DEFAULT VALUES;
--
2.34.1
--SywurcztURg2uk+W--
^ permalink raw reply [nested|flat] 10+ messages in thread
* [PATCH v3 1/3] Adding per backend commit and rollback counters
@ 2025-08-04 08:14 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-04 08:14 UTC (permalink / raw)
It relies on the existing per backend statistics that has been added in
9aea73fc61d. A new function is called in AtEOXact_PgStat() to increment those
two new counters.
---
src/backend/utils/activity/pgstat_backend.c | 57 +++++++++++++++++++++
src/backend/utils/activity/pgstat_xact.c | 1 +
src/include/pgstat.h | 8 +++
src/include/utils/pgstat_internal.h | 4 +-
4 files changed, 69 insertions(+), 1 deletion(-)
78.9% src/backend/utils/activity/
11.2% src/include/utils/
9.8% src/include/
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 8714a85e2d9..bf164854c4b 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -47,6 +47,11 @@ static bool backend_has_iostats = false;
*/
static WalUsage prevBackendWalUsage;
+/*
+ * For backend commit and rollback statistics.
+ */
+static bool backend_has_xactstats = false;
+
/*
* Utility routines to report I/O stats for backends, kept here to avoid
* exposing PendingBackendStats to the outside world.
@@ -259,6 +264,34 @@ pgstat_flush_backend_entry_wal(PgStat_EntryRef *entry_ref)
prevBackendWalUsage = pgWalUsage;
}
+/*
+ * Flush out locally pending backend transaction statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+
+ /*
+ * This function can be called even if nothing at all has happened for
+ * transaction statistics. In this case, avoid unnecessarily modifying
+ * the stats entry.
+ */
+ if (!backend_has_xactstats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+
+ shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
+ shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+
+ PendingBackendStats.pending_xact_commit = 0;
+ PendingBackendStats.pending_xact_rollback = 0;
+
+ backend_has_xactstats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -283,6 +316,10 @@ pgstat_flush_backend(bool nowait, bits32 flags)
pgstat_backend_wal_have_pending())
has_pending_data = true;
+ /* Some transaction data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -298,6 +335,9 @@ pgstat_flush_backend(bool nowait, bits32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_WAL)
pgstat_flush_backend_entry_wal(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_XACT)
+ pgstat_flush_backend_entry_xact(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -400,3 +440,20 @@ pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header, TimestampTz ts)
{
((PgStatShared_Backend *) header)->stats.stat_reset_timestamp = ts;
}
+
+void
+AtEOXact_PgStat_Backend(bool isCommit, bool parallel)
+{
+ /* Don't count parallel worker transaction stats */
+ if (!parallel)
+ {
+ /* Count transaction commit or abort */
+ if (isCommit)
+ PendingBackendStats.pending_xact_commit++;
+ else
+ PendingBackendStats.pending_xact_rollback++;
+
+ backend_has_xactstats = true;
+ pgstat_report_fixed = true;
+ }
+}
diff --git a/src/backend/utils/activity/pgstat_xact.c b/src/backend/utils/activity/pgstat_xact.c
index bc9864bd8d9..cd1c501c165 100644
--- a/src/backend/utils/activity/pgstat_xact.c
+++ b/src/backend/utils/activity/pgstat_xact.c
@@ -42,6 +42,7 @@ AtEOXact_PgStat(bool isCommit, bool parallel)
PgStat_SubXactStatus *xact_state;
AtEOXact_PgStat_Database(isCommit, parallel);
+ AtEOXact_PgStat_Backend(isCommit, parallel);
/* handle transactional stats information */
xact_state = pgStatXactStack;
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 202bd2d5ace..9efc0e10ebf 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -490,6 +490,8 @@ typedef struct PgStat_Backend
TimestampTz stat_reset_timestamp;
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
+ PgStat_Counter xact_commit;
+ PgStat_Counter xact_rollback;
} PgStat_Backend;
/* ---------
@@ -502,6 +504,12 @@ typedef struct PgStat_BackendPending
* Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
*/
PgStat_PendingIO pending_io;
+
+ /*
+ * Transaction statistics pending flush.
+ */
+ PgStat_Counter pending_xact_commit;
+ PgStat_Counter pending_xact_rollback;
} PgStat_BackendPending;
/*
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index 6cf00008f63..23ea8ffd618 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -616,12 +616,14 @@ extern void pgstat_archiver_snapshot_cb(void);
/* flags for pgstat_flush_backend() */
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL)
+#define PGSTAT_BACKEND_FLUSH_XACT (1 << 2) /* Flush xact statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_XACT)
extern bool pgstat_flush_backend(bool nowait, bits32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
extern void pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header,
TimestampTz ts);
+extern void AtEOXact_PgStat_Backend(bool isCommit, bool parallel);
/*
* Functions in pgstat_bgwriter.c
--
2.34.1
--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="v3-0002-Adding-XID-generation-count-per-backend.patch"
^ permalink raw reply [nested|flat] 10+ messages in thread
* [PATCH v1] Adding per backend commit and rollback counters
@ 2025-08-04 08:14 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-04 08:14 UTC (permalink / raw)
This commit adds 2 functions: pg_stat_get_backend_xact_commit() and
pg_stat_get_backend_xact_rollback() to report the number of transactions that
have been committed/rolled back for a given backend PID.
It relies on the existing per backend statistics that has been added in
9aea73fc61d.
---
doc/src/sgml/monitoring.sgml | 36 +++++++++++++
src/backend/utils/activity/pgstat_backend.c | 60 +++++++++++++++++++++
src/backend/utils/activity/pgstat_xact.c | 1 +
src/backend/utils/adt/pgstatfuncs.c | 22 ++++++++
src/include/catalog/pg_proc.dat | 9 ++++
src/include/pgstat.h | 2 +
src/include/utils/pgstat_internal.h | 4 +-
src/test/regress/expected/stats.out | 17 ++++++
src/test/regress/sql/stats.sql | 10 ++++
9 files changed, 160 insertions(+), 1 deletion(-)
26.9% doc/src/sgml/
29.1% src/backend/utils/activity/
12.3% src/backend/utils/adt/
9.7% src/include/catalog/
4.0% src/include/utils/
9.2% src/test/regress/expected/
7.3% src/test/regress/sql/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index fa78031ccbb..ef89683164f 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -4921,6 +4921,42 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-xact-commit" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_xact_commit</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_xact_commit</function> ( <type>integer</type> )
+ <returnvalue>bigint</returnvalue>
+ </para>
+ <para>
+ Returns the number of transactions that have been committed by the backend
+ with the specified process ID.
+ </para>
+ <para>
+ The function does not return statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
+ <row>
+ <entry id="pg-stat-get-backend-xact-rollback" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_xact_rollback</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_xact_rollback</function> ( <type>integer</type> )
+ <returnvalue>bigint</returnvalue>
+ </para>
+ <para>
+ Returns the number of transactions that have been rolled back by the backend
+ with the specified process ID.
+ </para>
+ <para>
+ The function does not return statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 8714a85e2d9..7cec0c83071 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -47,6 +47,13 @@ static bool backend_has_iostats = false;
*/
static WalUsage prevBackendWalUsage;
+/*
+ * For backend commit and rollback statistics.
+ */
+static int pgStatBackendXactCommit = 0;
+static int pgStatBackendXactRollback = 0;
+static bool backend_has_xactstats = false;
+
/*
* Utility routines to report I/O stats for backends, kept here to avoid
* exposing PendingBackendStats to the outside world.
@@ -259,6 +266,33 @@ pgstat_flush_backend_entry_wal(PgStat_EntryRef *entry_ref)
prevBackendWalUsage = pgWalUsage;
}
+/*
+ * Flush out locally pending backend xact statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+
+ /*
+ * This function can be called even if nothing at all has happened for
+ * XACT statistics. In this case, avoid unnecessarily modifying the stats
+ * entry.
+ */
+ if (!backend_has_xactstats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+
+ shbackendent->stats.xact_commit += pgStatBackendXactCommit;
+ shbackendent->stats.xact_rollback += pgStatBackendXactRollback;
+
+ pgStatBackendXactCommit = pgStatBackendXactRollback = 0;
+
+ backend_has_xactstats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -283,6 +317,10 @@ pgstat_flush_backend(bool nowait, bits32 flags)
pgstat_backend_wal_have_pending())
has_pending_data = true;
+ /* Some XACT data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -298,6 +336,9 @@ pgstat_flush_backend(bool nowait, bits32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_WAL)
pgstat_flush_backend_entry_wal(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_XACT)
+ pgstat_flush_backend_entry_xact(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -400,3 +441,22 @@ pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header, TimestampTz ts)
{
((PgStatShared_Backend *) header)->stats.stat_reset_timestamp = ts;
}
+
+void
+AtEOXact_PgStat_Backend(bool isCommit, bool parallel)
+{
+ /* Don't count parallel worker transaction stats */
+ if (!parallel)
+ {
+ /*
+ * Count transaction commit or abort. (We use counters, not just
+ * bools, in case the reporting message isn't sent right away.)
+ */
+ if (isCommit)
+ pgStatBackendXactCommit++;
+ else
+ pgStatBackendXactRollback++;
+
+ backend_has_xactstats = true;
+ }
+}
diff --git a/src/backend/utils/activity/pgstat_xact.c b/src/backend/utils/activity/pgstat_xact.c
index bc9864bd8d9..cd1c501c165 100644
--- a/src/backend/utils/activity/pgstat_xact.c
+++ b/src/backend/utils/activity/pgstat_xact.c
@@ -42,6 +42,7 @@ AtEOXact_PgStat(bool isCommit, bool parallel)
PgStat_SubXactStatus *xact_state;
AtEOXact_PgStat_Database(isCommit, parallel);
+ AtEOXact_PgStat_Backend(isCommit, parallel);
/* handle transactional stats information */
xact_state = pgStatXactStack;
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..6436129f516 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1606,6 +1606,28 @@ pg_stat_get_backend_io(PG_FUNCTION_ARGS)
return (Datum) 0;
}
+#define PG_STAT_GET_BACKENDENTRY_INT64(stat) \
+Datum \
+CppConcat(pg_stat_get_backend_,stat)(PG_FUNCTION_ARGS) \
+{ \
+ int pid; \
+ PgStat_Backend *backend_stats; \
+ \
+ pid = PG_GETARG_INT32(0); \
+ backend_stats = pgstat_fetch_stat_backend_by_pid(pid, NULL);\
+ \
+ if (!backend_stats) \
+ PG_RETURN_NULL(); \
+ else \
+ PG_RETURN_INT64(backend_stats->stat); \
+}
+
+/* pg_stat_get_backend_xact_commit */
+PG_STAT_GET_BACKENDENTRY_INT64(xact_commit)
+
+/* pg_stat_get_backend_xact_rollback */
+PG_STAT_GET_BACKENDENTRY_INT64(xact_rollback)
+
/*
* pg_stat_wal_build_tuple
*
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..f5085d4e016 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6010,6 +6010,15 @@
proargnames => '{backend_pid,backend_type,object,context,reads,read_bytes,read_time,writes,write_bytes,write_time,writebacks,writeback_time,extends,extend_bytes,extend_time,hits,evictions,reuses,fsyncs,fsync_time,stats_reset}',
prosrc => 'pg_stat_get_backend_io' },
+{ oid => '8170', descr => 'statistics: backend transactions committed',
+ proname => 'pg_stat_get_backend_xact_commit', provolatile => 's',
+ proparallel => 'r', prorettype => 'int8', proargtypes => 'int4',
+ prosrc => 'pg_stat_get_backend_xact_commit' },
+{ oid => '8916', descr => 'statistics: backend transactions rolled back',
+ proname => 'pg_stat_get_backend_xact_rollback', provolatile => 's',
+ proparallel => 'r', prorettype => 'int8', proargtypes => 'int4',
+ prosrc => 'pg_stat_get_backend_xact_rollback' },
+
{ oid => '1136', descr => 'statistics: information about WAL activity',
proname => 'pg_stat_get_wal', proisstrict => 'f', provolatile => 's',
proparallel => 'r', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 202bd2d5ace..4c9f6b0dcec 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -490,6 +490,8 @@ typedef struct PgStat_Backend
TimestampTz stat_reset_timestamp;
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
+ PgStat_Counter xact_commit;
+ PgStat_Counter xact_rollback;
} PgStat_Backend;
/* ---------
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index 6cf00008f63..23ea8ffd618 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -616,12 +616,14 @@ extern void pgstat_archiver_snapshot_cb(void);
/* flags for pgstat_flush_backend() */
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL)
+#define PGSTAT_BACKEND_FLUSH_XACT (1 << 2) /* Flush xact statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_XACT)
extern bool pgstat_flush_backend(bool nowait, bits32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
extern void pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header,
TimestampTz ts);
+extern void AtEOXact_PgStat_Backend(bool isCommit, bool parallel);
/*
* Functions in pgstat_bgwriter.c
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..0d316f94e40 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT pg_stat_get_backend_xact_commit AS xact_commit_before
+ FROM pg_stat_get_backend_xact_commit(pg_backend_pid()) \gset
BEGIN;
UPDATE trunc_stats_test1 SET id = id + 100;
TRUNCATE trunc_stats_test1;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush
+--------------------------
+
+(1 row)
+
+SELECT pg_stat_get_backend_xact_commit AS xact_commit_after
+ FROM pg_stat_get_backend_xact_commit(pg_backend_pid()) \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column?
+----------
+ t
+(1 row)
+
-- use a savepoint: 1 insert, 1 live
BEGIN;
INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..d629140d880 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT pg_stat_get_backend_xact_commit AS xact_commit_before
+ FROM pg_stat_get_backend_xact_commit(pg_backend_pid()) \gset
+
BEGIN;
UPDATE trunc_stats_test1 SET id = id + 100;
TRUNCATE trunc_stats_test1;
INSERT INTO trunc_stats_test1 DEFAULT VALUES;
COMMIT;
+SELECT pg_stat_force_next_flush();
+SELECT pg_stat_get_backend_xact_commit AS xact_commit_after
+ FROM pg_stat_get_backend_xact_commit(pg_backend_pid()) \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
-- use a savepoint: 1 insert, 1 live
BEGIN;
INSERT INTO trunc_stats_test2 DEFAULT VALUES;
--
2.34.1
--ZnbSmJtA6EgjuGCe--
^ permalink raw reply [nested|flat] 10+ messages in thread
* [PATCH v4 1/3] Adding per backend commit and rollback counters
@ 2025-08-04 08:14 Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-04 08:14 UTC (permalink / raw)
It relies on the existing per backend statistics that has been added in
9aea73fc61d. The new pending counters are updated when the database ones are
flushed (to reduce the overhead of incrementing new counters).
---
src/backend/utils/activity/pgstat_backend.c | 42 +++++++++++++++++++-
src/backend/utils/activity/pgstat_database.c | 7 ++++
src/include/pgstat.h | 15 +++++++
src/include/utils/pgstat_internal.h | 3 +-
4 files changed, 65 insertions(+), 2 deletions(-)
74.4% src/backend/utils/activity/
7.8% src/include/utils/
17.7% src/include/
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 8714a85e2d9..47ce61e5093 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -36,7 +36,7 @@
* reported within critical sections so we use static memory in order to avoid
* memory allocation.
*/
-static PgStat_BackendPending PendingBackendStats;
+PgStat_BackendPending PendingBackendStats;
static bool backend_has_iostats = false;
/*
@@ -47,6 +47,11 @@ static bool backend_has_iostats = false;
*/
static WalUsage prevBackendWalUsage;
+/*
+ * For backend commit and rollback statistics.
+ */
+bool backend_has_xactstats = false;
+
/*
* Utility routines to report I/O stats for backends, kept here to avoid
* exposing PendingBackendStats to the outside world.
@@ -259,6 +264,34 @@ pgstat_flush_backend_entry_wal(PgStat_EntryRef *entry_ref)
prevBackendWalUsage = pgWalUsage;
}
+/*
+ * Flush out locally pending backend transaction statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+
+ /*
+ * This function can be called even if nothing at all has happened for
+ * transaction statistics. In this case, avoid unnecessarily modifying
+ * the stats entry.
+ */
+ if (!backend_has_xactstats)
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+
+ shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
+ shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+
+ PendingBackendStats.pending_xact_commit = 0;
+ PendingBackendStats.pending_xact_rollback = 0;
+
+ backend_has_xactstats = false;
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -283,6 +316,10 @@ pgstat_flush_backend(bool nowait, bits32 flags)
pgstat_backend_wal_have_pending())
has_pending_data = true;
+ /* Some transaction data pending? */
+ if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+ has_pending_data = true;
+
if (!has_pending_data)
return false;
@@ -298,6 +335,9 @@ pgstat_flush_backend(bool nowait, bits32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_WAL)
pgstat_flush_backend_entry_wal(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_XACT)
+ pgstat_flush_backend_entry_xact(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
diff --git a/src/backend/utils/activity/pgstat_database.c b/src/backend/utils/activity/pgstat_database.c
index b31f20d41bc..400a8c5d734 100644
--- a/src/backend/utils/activity/pgstat_database.c
+++ b/src/backend/utils/activity/pgstat_database.c
@@ -342,6 +342,13 @@ pgstat_update_dbstats(TimestampTz ts)
dbentry->blk_read_time += pgStatBlockReadTime;
dbentry->blk_write_time += pgStatBlockWriteTime;
+ /* Do the same for backend stats */
+ PendingBackendStats.pending_xact_commit += pgStatXactCommit;
+ PendingBackendStats.pending_xact_rollback += pgStatXactRollback;
+
+ backend_has_xactstats = true;
+ pgstat_report_fixed = true;
+
if (pgstat_should_report_connstat())
{
long secs;
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 202bd2d5ace..0fdbaf79780 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -490,6 +490,8 @@ typedef struct PgStat_Backend
TimestampTz stat_reset_timestamp;
PgStat_BktypeIO io_stats;
PgStat_WalCounters wal_counters;
+ PgStat_Counter xact_commit;
+ PgStat_Counter xact_rollback;
} PgStat_Backend;
/* ---------
@@ -502,6 +504,12 @@ typedef struct PgStat_BackendPending
* Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
*/
PgStat_PendingIO pending_io;
+
+ /*
+ * Transaction statistics pending flush.
+ */
+ PgStat_Counter pending_xact_commit;
+ PgStat_Counter pending_xact_rollback;
} PgStat_BackendPending;
/*
@@ -801,6 +809,13 @@ extern PGDLLIMPORT int pgstat_track_functions;
extern PGDLLIMPORT int pgstat_fetch_consistency;
+/*
+ * Variables in pgstat_backend.c
+ */
+
+extern PGDLLIMPORT PgStat_BackendPending PendingBackendStats;
+extern PGDLLIMPORT bool backend_has_xactstats;
+
/*
* Variables in pgstat_bgwriter.c
*/
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index 6cf00008f63..b97184c6539 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -616,7 +616,8 @@ extern void pgstat_archiver_snapshot_cb(void);
/* flags for pgstat_flush_backend() */
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL)
+#define PGSTAT_BACKEND_FLUSH_XACT (1 << 2) /* Flush xact statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL | PGSTAT_BACKEND_FLUSH_XACT)
extern bool pgstat_flush_backend(bool nowait, bits32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
--
2.34.1
--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="v4-0002-Adding-XID-generation-count-per-backend.patch"
^ permalink raw reply [nested|flat] 10+ messages in thread
* Adding per backend commit and rollback counters
@ 2025-08-04 14:20 Bertrand Drouvot <[email protected]>
2025-08-07 08:17 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
0 siblings, 1 reply; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-04 14:20 UTC (permalink / raw)
To: PostgreSQL Hackers <[email protected]>
Hi hackers,
PFA a patch for $SUBJECT.
Currently we can find xact_commit and xact_rollback in pg_stat_database but we
don't have this information per backend.
This patch adds 2 functions: pg_stat_get_backend_xact_commit() and
pg_stat_get_backend_xact_rollback() to report the number of transactions that
have been committed/rolled back for a given backend PID.
I think having this information per-backend could be useful, for example, to:
- check which application is producing the highest number of commit / rollback
- check if the application's hosts have "uniform" commit/rollback pattern
- check if some application's hosts are doing a lot of rollback (as compared
to the other hosts): that could mean those hosts are not using an up-to-date
application version
This patch is pretty straightforward as it relies on the existing per backend
statistics machinery that has been added in 9aea73fc61d (so that there is not
that much design to discuss).
On a side note, I noticed that when a transaction fails, say this way:
postgres=# insert into bdt2 values(1);
ERROR: relation "bdt2" does not exist
Then the existing pg_stat_get_db_xact_rollback() does not return the rollback
increment (so does pg_stat_database.xact_rollback). Indeed, the flush is done
during the next commit or explicit rollback.
Maybe we could add an extra counter, that tracks the transactions that have not
been explicitly rolled back (xact_error or such) and flush it at the right time.
Looking forward to your feedback,
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 10+ messages in thread
* Re: Adding per backend commit and rollback counters
2025-08-04 14:20 Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
@ 2025-08-07 08:17 ` Bertrand Drouvot <[email protected]>
2025-08-10 07:47 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
0 siblings, 1 reply; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-07 08:17 UTC (permalink / raw)
To: PostgreSQL Hackers <[email protected]>
Hi,
On Mon, Aug 04, 2025 at 02:20:48PM +0000, Bertrand Drouvot wrote:
> This patch is pretty straightforward as it relies on the existing per backend
> statistics machinery that has been added in 9aea73fc61d (so that there is not
> that much design to discuss).
Still, while working on adding more backend stats (more on that later), I
realized that in v1, I missed to use pgstat_report_fixed (recently added in
793928c2d5a): the attached fixes that.
Also, I think it's better to put the new xact pending counters in the existing
PgStat_BackendPending, done that way in the attached.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 10+ messages in thread
* Re: Adding per backend commit and rollback counters
2025-08-04 14:20 Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
2025-08-07 08:17 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
@ 2025-08-10 07:47 ` Bertrand Drouvot <[email protected]>
2025-08-28 16:07 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
0 siblings, 1 reply; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-10 07:47 UTC (permalink / raw)
To: PostgreSQL Hackers <[email protected]>
Hi,
On Thu, Aug 07, 2025 at 08:17:26AM +0000, Bertrand Drouvot wrote:
> Hi,
>
> On Mon, Aug 04, 2025 at 02:20:48PM +0000, Bertrand Drouvot wrote:
> > This patch is pretty straightforward as it relies on the existing per backend
> > statistics machinery that has been added in 9aea73fc61d (so that there is not
> > that much design to discuss).
>
> Still, while working on adding more backend stats (more on that later), I
> realized that in v1, I missed to use pgstat_report_fixed (recently added in
> 793928c2d5a): the attached fixes that.
>
> Also, I think it's better to put the new xact pending counters in the existing
> PgStat_BackendPending, done that way in the attached.
Another metric that could be useful is to track the XIDs generated by backend.
That would help to see if a backend is consuming XIDs at a high rate.
We can not rely on the number of commits or rollbacks as they take into account
the virtual transactions.
So a new counter has been added in 0002 attached. Also, v3 changes the way
the statistics are displayed. I've in mind to add much more statistics per backend
(such a number of seqscans, vacuum count, analyze count..., I'll open a dedicated
thread for those) and I think that a single view to display them all makes
more sense than a lot of individual functions. This view is added in 0003.
To sum up, v3 contains:
0001 -
Adding per backend commit and rollback counters
It relies on the existing per backend statistics that has been added in
9aea73fc61d. A new function is called in AtEOXact_PgStat() to increment those
two new counters.
0002 -
Adding XID generation count per backend
This patch adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.
Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
0003 -
Adding the pg_stat_backend view
This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.
It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().
Adding documentation and tests.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 10+ messages in thread
* Re: Adding per backend commit and rollback counters
2025-08-04 14:20 Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
2025-08-07 08:17 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
2025-08-10 07:47 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
@ 2025-08-28 16:07 ` Bertrand Drouvot <[email protected]>
2026-03-31 09:24 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
0 siblings, 1 reply; 10+ messages in thread
From: Bertrand Drouvot @ 2025-08-28 16:07 UTC (permalink / raw)
To: PostgreSQL Hackers <[email protected]>
Hi,
On Sun, Aug 10, 2025 at 07:47:09AM +0000, Bertrand Drouvot wrote:
> To sum up, v3 contains:
>
> 0001 -
> Adding per backend commit and rollback counters
> 0002 -
> Adding XID generation count per backend
> 0003 -
> Adding the pg_stat_backend view
Following recent conversations in [1], those changes have been made in v4
attached:
- avoid tracking the commit and rollback counters twice (for databases and for
backends) but increment the backend stats when the database ones are flushed. Same
idea as [2].
- pg_stat_backend is too generic (see [3]), let's use pg_stat_backend_transaction
instead. I deliberately did not use pg_stat_backend_xact to not confuse with the
other "*xact*" functions/views where the meaning is not the same. I'm open to
other naming suggestion though.
[1]: https://www.postgresql.org/message-id/flat/aJrxug4LCg4Hm5Mm%40ip-10-97-1-34.eu-west-3.compute.intern...
[2]: https://www.postgresql.org/message-id/7fhpds4xqk6bnudzmzkqi33pinsxammpljwde5gfkjdygvejrj%40ojkzfr7dx...
[3]: https://www.postgresql.org/message-id/aK8OuVPmmDTc9CFX%40ip-10-97-1-34.eu-west-3.compute.internal
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 10+ messages in thread
* Re: Adding per backend commit and rollback counters
2025-08-04 14:20 Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
2025-08-07 08:17 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
2025-08-10 07:47 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
2025-08-28 16:07 ` Re: Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
@ 2026-03-31 09:24 ` Bertrand Drouvot <[email protected]>
0 siblings, 0 replies; 10+ messages in thread
From: Bertrand Drouvot @ 2026-03-31 09:24 UTC (permalink / raw)
To: Kuba Knysiak <[email protected]>; +Cc: [email protected]
Hi,
On Mon, Mar 30, 2026 at 08:19:13PM +0000, Kuba Knysiak wrote:
> Hello,
> after reviewing the patch together with Miłosz, we found the following:
Thanks for the review!
> - In pgstatfuncs.c, we call pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL)
> for each backend row. That path acquires ProcArrayLock via BackendPidGetProc(),
> so this repeats lock acquisition for every row. We could simplify this and avoid
> taking the lock altogether by fetching directly with
> pgstat_fetch_stat_backend(local_beentry->proc_number).
Yeah, I think that's a good point. Done that way in the attached. Also adding a
check on the backend type as it was done in pgstat_fetch_stat_backend_by_pid().
> Also, shouldn't this patch bump catversion?
Yes and that was mentioned in the 0003 commit message. We usually don't change
it in the patch itself (could easily produce rebase noise) but just put an
XXX in the commit message so that it's not forgoten when pushed.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
^ permalink raw reply [nested|flat] 10+ messages in thread
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2025-08-04 08:14 [PATCH v5 1/3] Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
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2025-08-04 14:20 Adding per backend commit and rollback counters Bertrand Drouvot <[email protected]>
2025-08-07 08:17 ` Bertrand Drouvot <[email protected]>
2025-08-10 07:47 ` Bertrand Drouvot <[email protected]>
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