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help / color / mirror / Atom feedFrom: Bertrand Drouvot <[email protected]>
Subject: [PATCH v1 2/2] Add the pg_stat_lock view
Date: Thu, 31 Jul 2025 09:35:31 +0000
This new view reports lock statistics.
This commit also adds documentation and a few tests.
XXX: Bump catversion
---
doc/src/sgml/monitoring.sgml | 151 ++++++++++++++++++
src/backend/catalog/system_views.sql | 12 ++
src/backend/utils/activity/pgstat_lock.c | 8 +
src/backend/utils/adt/pgstatfuncs.c | 39 +++++
src/include/catalog/pg_proc.dat | 9 ++
src/include/pgstat.h | 1 +
src/test/isolation/expected/deadlock-hard.out | 20 ++-
src/test/isolation/specs/deadlock-hard.spec | 5 +-
src/test/regress/expected/advisory_lock.out | 18 +++
src/test/regress/expected/rules.out | 9 ++
src/test/regress/sql/advisory_lock.sql | 4 +
11 files changed, 274 insertions(+), 2 deletions(-)
51.5% doc/src/sgml/
3.3% src/backend/catalog/
14.3% src/backend/utils/adt/
5.7% src/include/catalog/
8.4% src/test/isolation/expected/
5.9% src/test/isolation/specs/
6.7% src/test/regress/expected/
3.8% src/
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 823afe1b30b..0d18124f239 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -493,6 +493,15 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
</entry>
</row>
+ <row>
+ <entry><structname>pg_stat_lock</structname><indexterm><primary>pg_stat_lock</primary></indexterm></entry>
+ <entry>
+ One row for each lock type, containing cluster-wide locks statistics.
+ See <link linkend="monitoring-pg-stat-lock-view">
+ <structname>pg_stat_lock</structname></link> for details.
+ </entry>
+ </row>
+
<row>
<entry><structname>pg_stat_replication_slots</structname><indexterm><primary>pg_stat_replication_slots</primary></indexterm></entry>
<entry>One row per replication slot, showing statistics about the
@@ -3027,6 +3036,142 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</sect2>
+
+ <sect2 id="monitoring-pg-stat-lock-view">
+ <title><structname>pg_stat_lock</structname></title>
+
+ <indexterm>
+ <primary>pg_stat_lock</primary>
+ </indexterm>
+
+ <para>
+ The <structname>pg_stat_lock</structname> view will contain one row for each
+ lock type, showing cluster-wide locks statistics.
+ </para>
+
+ <table id="pg-stat-lock-view" xreflabel="pg_stat_lock">
+ <title><structname>pg_stat_lock</structname> View</title>
+ <tgroup cols="1">
+ <thead>
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ Column Type
+ </para>
+ <para>
+ Description
+ </para>
+ </entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ <structfield>locktype</structfield> <type>text</type>
+ </para>
+ <para>
+ Type of the lockable object:
+ <literal>relation</literal>,
+ <literal>extend</literal>,
+ <literal>frozenid</literal>,
+ <literal>page</literal>,
+ <literal>tuple</literal>,
+ <literal>transactionid</literal>,
+ <literal>virtualxid</literal>,
+ <literal>spectoken</literal>,
+ <literal>object</literal>,
+ <literal>userlock</literal>,
+ <literal>advisory</literal>, or
+ <literal>applytransaction</literal>.
+ (See also <xref linkend="wait-event-lock-table"/>.)
+ </para>
+ </entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ <structfield>requests</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of requests for this lock type.
+ </para>
+ </entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ <structfield>waits</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of times requests for this lock type had to wait.
+ </para>
+ </entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ <structfield>timeouts</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of times requests for this lock type had to wait longer
+ than <varname>lock_timeout</varname>.
+ </para>
+ </entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ <structfield>deadlock_timeouts</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of times requests for this lock type had to wait longer
+ than <varname>deadlock_timeout</varname>.
+ </para>
+ </entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ <structfield>deadlocks</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of times a deadlock occurred on this lock type.
+ </para>
+ </entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ <structfield>fastpath</structfield> <type>bigint</type>
+ </para>
+ <para>
+ Number of times this lock type was taken via fast path.
+ </para>
+ </entry>
+ </row>
+
+ <row>
+ <entry role="catalog_table_entry">
+ <para role="column_definition">
+ <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+ </para>
+ <para>
+ Time at which these statistics were last reset.
+ </para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+ </sect2>
+
<sect2 id="monitoring-pg-stat-bgwriter-view">
<title><structname>pg_stat_bgwriter</structname></title>
@@ -5044,6 +5189,12 @@ description | Waiting for a newly initialized WAL file to reach durable storage
<structname>pg_stat_io</structname> view.
</para>
</listitem>
+ <listitem>
+ <para>
+ <literal>lock</literal>: Reset all the counters shown in the
+ <structname>pg_stat_lock</structname> view.
+ </para>
+ </listitem>
<listitem>
<para>
<literal>recovery_prefetch</literal>: Reset all the counters shown in
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index f6eca09ee15..d493a00c544 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -950,6 +950,18 @@ CREATE VIEW pg_stat_slru AS
s.stats_reset
FROM pg_stat_get_slru() s;
+CREATE VIEW pg_stat_lock AS
+ SELECT
+ l.locktype,
+ l.requests,
+ l.waits,
+ l.timeouts,
+ l.deadlock_timeouts,
+ l.deadlocks,
+ l.fastpath,
+ l.stats_reset
+ FROM pg_stat_get_lock() l;
+
CREATE VIEW pg_stat_wal_receiver AS
SELECT
s.pid,
diff --git a/src/backend/utils/activity/pgstat_lock.c b/src/backend/utils/activity/pgstat_lock.c
index fb4ed5c7362..73bdeb5ff66 100644
--- a/src/backend/utils/activity/pgstat_lock.c
+++ b/src/backend/utils/activity/pgstat_lock.c
@@ -21,6 +21,14 @@
static PgStat_PendingLock PendingLockStats;
static bool have_lockstats = false;
+PgStat_Lock *
+pgstat_fetch_stat_lock(void)
+{
+ pgstat_snapshot_fixed(PGSTAT_KIND_LOCK);
+
+ return &pgStatLocal.snapshot.lock;
+}
+
/*
* Simpler wrapper of pgstat_lock_flush_cb()
*/
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 1c12ddbae49..5e63f2d2a38 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1696,6 +1696,42 @@ pg_stat_get_wal(PG_FUNCTION_ARGS)
wal_stats->stat_reset_timestamp));
}
+Datum
+pg_stat_get_lock(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_LOCK_COLS 8
+ ReturnSetInfo *rsinfo;
+ PgStat_Lock *lock_stats;
+
+ InitMaterializedSRF(fcinfo, 0);
+ rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+ lock_stats = pgstat_fetch_stat_lock();
+
+ for (int lcktype = 0; lcktype <= LOCKTAG_LAST_TYPE; lcktype++)
+ {
+ const char *locktypename;
+ Datum values[PG_STAT_LOCK_COLS] = {0};
+ bool nulls[PG_STAT_LOCK_COLS] = {0};
+ PgStat_LockEntry *lck_stats = &lock_stats->stats[lcktype];
+
+ locktypename = LockTagTypeNames[lcktype];
+
+ values[0] = CStringGetTextDatum(locktypename);
+ values[1] = Int64GetDatum(lck_stats->requests);
+ values[2] = Int64GetDatum(lck_stats->waits);
+ values[3] = Int64GetDatum(lck_stats->timeouts);
+ values[4] = Int64GetDatum(lck_stats->deadlock_timeouts);
+ values[5] = Int64GetDatum(lck_stats->deadlocks);
+ values[6] = Int64GetDatum(lck_stats->fastpath);
+ values[7] = TimestampTzGetDatum(lock_stats->stat_reset_timestamp);
+
+ tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+ }
+
+ return (Datum) 0;
+}
+
/*
* Returns statistics of SLRU caches.
*/
@@ -1880,6 +1916,7 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
pgstat_reset_of_kind(PGSTAT_KIND_IO);
+ pgstat_reset_of_kind(PGSTAT_KIND_LOCK);
XLogPrefetchResetStats();
pgstat_reset_of_kind(PGSTAT_KIND_SLRU);
pgstat_reset_of_kind(PGSTAT_KIND_WAL);
@@ -1897,6 +1934,8 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
else if (strcmp(target, "io") == 0)
pgstat_reset_of_kind(PGSTAT_KIND_IO);
+ else if (strcmp(target, "lock") == 0)
+ pgstat_reset_of_kind(PGSTAT_KIND_LOCK);
else if (strcmp(target, "recovery_prefetch") == 0)
XLogPrefetchResetStats();
else if (strcmp(target, "slru") == 0)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 3ee8fed7e53..c5faff30317 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -6001,6 +6001,15 @@
proargnames => '{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_io' },
+{ oid => '9375', descr => 'statistics: per lock type statistics',
+ proname => 'pg_stat_get_lock', prorows => '10', proretset => 't',
+ provolatile => 'v', proparallel => 'r', prorettype => 'record',
+ proargtypes => '',
+ proallargtypes => '{text,int8,int8,int8,int8,int8,int8,timestamptz}',
+ proargmodes => '{o,o,o,o,o,o,o,o}',
+ proargnames => '{locktype,requests,waits,timeouts,deadlock_timeouts,deadlocks,fastpath,stats_reset}',
+ prosrc => 'pg_stat_get_lock' },
+
{ oid => '6386', descr => 'statistics: backend IO statistics',
proname => 'pg_stat_get_backend_io', prorows => '5', proretset => 't',
provolatile => 'v', proparallel => 'r', prorettype => 'record',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 7893f7311ae..e653bce4aab 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -636,6 +636,7 @@ extern void pgstat_count_lock_timeouts(uint8 locktag_type);
extern void pgstat_count_lock_deadlock_timeouts(uint8 locktag_type);
extern void pgstat_count_lock_deadlocks(uint8 locktag_type);
extern void pgstat_count_lock_fastpath(uint8 locktag_type);
+extern PgStat_Lock *pgstat_fetch_stat_lock(void);
/*
* Functions in pgstat_database.c
diff --git a/src/test/isolation/expected/deadlock-hard.out b/src/test/isolation/expected/deadlock-hard.out
index 460653f2b86..ff448da5299 100644
--- a/src/test/isolation/expected/deadlock-hard.out
+++ b/src/test/isolation/expected/deadlock-hard.out
@@ -1,6 +1,12 @@
Parsed test spec with 8 sessions
-starting permutation: s1a1 s2a2 s3a3 s4a4 s5a5 s6a6 s7a7 s8a8 s1a2 s2a3 s3a4 s4a5 s5a6 s6a7 s7a8 s8a1 s8c s7c s6c s5c s4c s3c s2c s1c
+starting permutation: s1rl s1a1 s2a2 s3a3 s4a4 s5a5 s6a6 s7a7 s8a8 s1a2 s2a3 s3a4 s4a5 s5a6 s6a7 s7a8 s8a1 s8c s8f s7c s6c s5c s4c s3c s2c s1c s1sl
+step s1rl: SELECT pg_stat_reset_shared('lock');
+pg_stat_reset_shared
+--------------------
+
+(1 row)
+
step s1a1: LOCK TABLE a1;
step s2a2: LOCK TABLE a2;
step s3a3: LOCK TABLE a3;
@@ -21,6 +27,12 @@ step s8a1: <... completed>
ERROR: deadlock detected
step s7a8: <... completed>
step s8c: COMMIT;
+step s8f: SELECT pg_stat_force_next_flush();
+pg_stat_force_next_flush
+------------------------
+
+(1 row)
+
step s7c: COMMIT;
step s6a7: <... completed>
step s6c: COMMIT;
@@ -34,3 +46,9 @@ step s2a3: <... completed>
step s2c: COMMIT;
step s1a2: <... completed>
step s1c: COMMIT;
+step s1sl: SELECT deadlocks > 0, deadlock_timeouts > 0 FROM pg_stat_lock WHERE locktype = 'relation';
+?column?|?column?
+--------+--------
+t |t
+(1 row)
+
diff --git a/src/test/isolation/specs/deadlock-hard.spec b/src/test/isolation/specs/deadlock-hard.spec
index 60bedca237a..6e8330662b4 100644
--- a/src/test/isolation/specs/deadlock-hard.spec
+++ b/src/test/isolation/specs/deadlock-hard.spec
@@ -25,6 +25,8 @@ setup { BEGIN; SET deadlock_timeout = '100s'; }
step s1a1 { LOCK TABLE a1; }
step s1a2 { LOCK TABLE a2; }
step s1c { COMMIT; }
+step s1sl { SELECT deadlocks > 0, deadlock_timeouts > 0 FROM pg_stat_lock WHERE locktype = 'relation'; }
+step s1rl { SELECT pg_stat_reset_shared('lock'); }
session s2
setup { BEGIN; SET deadlock_timeout = '100s'; }
@@ -67,6 +69,7 @@ setup { BEGIN; SET deadlock_timeout = '10ms'; }
step s8a8 { LOCK TABLE a8; }
step s8a1 { LOCK TABLE a1; }
step s8c { COMMIT; }
+step s8f { SELECT pg_stat_force_next_flush(); }
# Note: when s8a1 detects the deadlock and fails, s7a8 is released, making
# it timing-dependent which query completion is received first by the tester.
@@ -76,4 +79,4 @@ step s8c { COMMIT; }
# dummy blocking mark to s8a1 to ensure it will be reported as "waiting"
# regardless of that.
-permutation s1a1 s2a2 s3a3 s4a4 s5a5 s6a6 s7a7 s8a8 s1a2 s2a3 s3a4 s4a5 s5a6 s6a7 s7a8(s8a1) s8a1(*) s8c s7c s6c s5c s4c s3c s2c s1c
+permutation s1rl s1a1 s2a2 s3a3 s4a4 s5a5 s6a6 s7a7 s8a8 s1a2 s2a3 s3a4 s4a5 s5a6 s6a7 s7a8(s8a1) s8a1(*) s8c s8f s7c s6c s5c s4c s3c s2c s1c s1sl
diff --git a/src/test/regress/expected/advisory_lock.out b/src/test/regress/expected/advisory_lock.out
index 02e07765ac2..fdaa1756ba4 100644
--- a/src/test/regress/expected/advisory_lock.out
+++ b/src/test/regress/expected/advisory_lock.out
@@ -2,6 +2,12 @@
-- ADVISORY LOCKS
--
SELECT oid AS datoid FROM pg_database WHERE datname = current_database() \gset
+SELECT pg_stat_reset_shared('lock');
+ pg_stat_reset_shared
+----------------------
+
+(1 row)
+
BEGIN;
SELECT
pg_advisory_xact_lock(1), pg_advisory_xact_lock_shared(2),
@@ -48,6 +54,12 @@ WARNING: you don't own a lock of type ShareLock
f | f | f | f
(1 row)
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush
+--------------------------
+
+(1 row)
+
-- automatically release xact locks at commit
COMMIT;
SELECT count(*) FROM pg_locks WHERE locktype = 'advisory' AND database = :datoid;
@@ -56,6 +68,12 @@ SELECT count(*) FROM pg_locks WHERE locktype = 'advisory' AND database = :datoid
0
(1 row)
+SELECT requests FROM pg_stat_lock WHERE locktype = 'advisory';
+ requests
+----------
+ 4
+(1 row)
+
BEGIN;
-- holding both session and xact locks on the same objects, xact first
SELECT
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index dce8c672b40..c790164ea82 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1938,6 +1938,15 @@ pg_stat_io| SELECT backend_type,
fsync_time,
stats_reset
FROM pg_stat_get_io() b(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);
+pg_stat_lock| SELECT locktype,
+ requests,
+ waits,
+ timeouts,
+ deadlock_timeouts,
+ deadlocks,
+ fastpath,
+ stats_reset
+ FROM pg_stat_get_lock() l(locktype, requests, waits, timeouts, deadlock_timeouts, deadlocks, fastpath, stats_reset);
pg_stat_progress_analyze| SELECT s.pid,
s.datid,
d.datname,
diff --git a/src/test/regress/sql/advisory_lock.sql b/src/test/regress/sql/advisory_lock.sql
index 8513ab8e98f..f1bff60fd37 100644
--- a/src/test/regress/sql/advisory_lock.sql
+++ b/src/test/regress/sql/advisory_lock.sql
@@ -4,6 +4,8 @@
SELECT oid AS datoid FROM pg_database WHERE datname = current_database() \gset
+SELECT pg_stat_reset_shared('lock');
+
BEGIN;
SELECT
@@ -26,12 +28,14 @@ SELECT
pg_advisory_unlock(1), pg_advisory_unlock_shared(2),
pg_advisory_unlock(1, 1), pg_advisory_unlock_shared(2, 2);
+SELECT pg_stat_force_next_flush();
-- automatically release xact locks at commit
COMMIT;
SELECT count(*) FROM pg_locks WHERE locktype = 'advisory' AND database = :datoid;
+SELECT requests FROM pg_stat_lock WHERE locktype = 'advisory';
BEGIN;
--
2.34.1
--Th7cMauVQntl/Hn1--
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