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help / color / mirror / Atom feedFrom: Bertrand Drouvot <[email protected]>
Subject: [PATCH v7 3/5] Add GUC to specify non-transactional statistics flush interval
Date: Wed, 28 Jan 2026 07:53:13 +0000
Adding pgstat_flush_interval, a new GUC to set the interval between flushes of
non-transactional statistics.
---
doc/src/sgml/config.sgml | 32 +++++++++++++++++++
src/backend/utils/activity/pgstat.c | 16 ++++++++++
src/backend/utils/misc/guc_parameters.dat | 10 ++++++
src/backend/utils/misc/postgresql.conf.sample | 1 +
src/include/pgstat.h | 6 ++--
src/include/utils/guc_hooks.h | 1 +
.../test_custom_stats/t/001_custom_stats.pl | 6 ++--
7 files changed, 66 insertions(+), 6 deletions(-)
51.8% doc/src/sgml/
13.3% src/backend/utils/activity/
13.6% src/backend/utils/misc/
11.3% src/include/
9.8% src/test/modules/test_custom_stats/t/
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 6bc2690ce07..383bbe3a132 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -8923,6 +8923,38 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
</listitem>
</varlistentry>
+ <varlistentry id="guc-stats-flush-interval" xreflabel="stats_flush_interval">
+ <term><varname>stats_flush_interval</varname> (<type>integer</type>)
+ <indexterm>
+ <primary><varname>stats_flush_interval</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Sets the interval at which certain statistics, which can be updated while a
+ transaction is in progress, are made visible. These include WAL activity
+ and I/O operations.
+ Such statistics are refreshed at the specified interval and can be observed
+ during active transactions in monitoring views such as
+ <link linkend="monitoring-pg-stat-wal-view"><structname>pg_stat_wal</structname></link>
+ and
+ <link linkend="monitoring-pg-stat-io-view"><structname>pg_stat_io</structname></link>.
+ If the value is specified without a unit, milliseconds are assumed.
+ The default is 10 seconds (<literal>10s</literal>), which is generally
+ the smallest practical value for long-running transactions.
+ </para>
+ <note>
+ <para>
+ This parameter does not affect statistics that are only reported at
+ transaction end, such as the columns of <structname>pg_stat_all_tables</structname>
+ (for example, <structfield>n_tup_ins</structfield>, <structfield>n_tup_upd</structfield>,
+ and <structfield>n_tup_del</structfield>). These statistics are always
+ flushed at the end of a transaction.
+ </para>
+ </note>
+ </listitem>
+ </varlistentry>
+
</variablelist>
</sect2>
diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index a4ff64dc5ce..dd85a27c52f 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -123,6 +123,8 @@
* ----------
*/
+/* minimum interval non-forced stats flushes.*/
+#define PGSTAT_MIN_INTERVAL 1000
/* how long until to block flushing pending stats updates */
#define PGSTAT_MAX_INTERVAL 60000
/* when to call pgstat_report_stat() again, even when idle */
@@ -203,6 +205,7 @@ static inline bool pgstat_is_kind_valid(PgStat_Kind kind);
bool pgstat_track_counts = false;
int pgstat_fetch_consistency = PGSTAT_FETCH_CONSISTENCY_CACHE;
+int pgstat_flush_interval = 10000;
/* ----------
@@ -2164,6 +2167,19 @@ assign_stats_fetch_consistency(int newval, void *extra)
force_stats_snapshot_clear = true;
}
+/*
+ * GUC assign_hook for stats_flush_interval.
+ */
+void
+assign_stats_flush_interval(int newval, void *extra)
+{
+ if (get_timeout_active(ANYTIME_STATS_UPDATE_TIMEOUT))
+ {
+ disable_timeout(ANYTIME_STATS_UPDATE_TIMEOUT, false);
+ enable_timeout_after(ANYTIME_STATS_UPDATE_TIMEOUT, newval);
+ }
+}
+
/*
* Flushes only FLUSH_ANYTIME stats using non-blocking locks. Transactional
* stats (FLUSH_AT_TXN_BOUNDARY) remain pending until transaction boundary.
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 271c033952e..d2734caafea 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -2801,6 +2801,16 @@
assign_hook => 'assign_stats_fetch_consistency',
},
+{ name => 'stats_flush_interval', type => 'int', context => 'PGC_USERSET', group => 'STATS_CUMULATIVE',
+ short_desc => 'Sets the interval between flushes of non-transactional statistics.',
+ flags => 'GUC_UNIT_MS',
+ variable => 'pgstat_flush_interval',
+ boot_val => '10000',
+ min => '1000',
+ max => 'INT_MAX',
+ assign_hook => 'assign_stats_flush_interval'
+},
+
{ name => 'subtransaction_buffers', type => 'int', context => 'PGC_POSTMASTER', group => 'RESOURCES_MEM',
short_desc => 'Sets the size of the dedicated buffer pool used for the subtransaction cache.',
long_desc => '0 means use a fraction of "shared_buffers".',
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index f938cc65a3a..8bd37a25b38 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -688,6 +688,7 @@
#track_wal_io_timing = off
#track_functions = none # none, pl, all
#stats_fetch_consistency = cache # cache, none, snapshot
+#stats_flush_interval = 10s # in milliseconds
# - Monitoring -
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index b340a680614..ef856dbf55b 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -35,9 +35,6 @@
/* Default directory to store temporary statistics data in */
#define PG_STAT_TMP_DIR "pg_stat_tmp"
-/* Minimum interval non-forced stats flushes */
-#define PGSTAT_MIN_INTERVAL 1000
-
/* Values for track_functions GUC variable --- order is significant! */
typedef enum TrackFunctionsLevel
{
@@ -548,7 +545,7 @@ extern void pgstat_force_next_flush(void);
#define pgstat_schedule_anytime_update() \
do { \
if (IsUnderPostmaster && !get_timeout_active(ANYTIME_STATS_UPDATE_TIMEOUT)) \
- enable_timeout_after(ANYTIME_STATS_UPDATE_TIMEOUT, PGSTAT_MIN_INTERVAL); \
+ enable_timeout_after(ANYTIME_STATS_UPDATE_TIMEOUT, pgstat_flush_interval); \
} while (0)
extern void pgstat_reset_counters(void);
@@ -828,6 +825,7 @@ extern PgStat_WalStats *pgstat_fetch_stat_wal(void);
extern PGDLLIMPORT bool pgstat_track_counts;
extern PGDLLIMPORT int pgstat_track_functions;
extern PGDLLIMPORT int pgstat_fetch_consistency;
+extern PGDLLIMPORT int pgstat_flush_interval;
/*
diff --git a/src/include/utils/guc_hooks.h b/src/include/utils/guc_hooks.h
index 9c90670d9b8..9b5d2a90387 100644
--- a/src/include/utils/guc_hooks.h
+++ b/src/include/utils/guc_hooks.h
@@ -132,6 +132,7 @@ extern bool check_session_authorization(char **newval, void **extra, GucSource s
extern void assign_session_authorization(const char *newval, void *extra);
extern void assign_session_replication_role(int newval, void *extra);
extern void assign_stats_fetch_consistency(int newval, void *extra);
+extern void assign_stats_flush_interval(int newval, void *extra);
extern bool check_ssl(bool *newval, void **extra, GucSource source);
extern bool check_stage_log_stats(bool *newval, void **extra, GucSource source);
extern bool check_standard_conforming_strings(bool *newval, void **extra,
diff --git a/src/test/modules/test_custom_stats/t/001_custom_stats.pl b/src/test/modules/test_custom_stats/t/001_custom_stats.pl
index 7be1b281776..22e2a75dcb9 100644
--- a/src/test/modules/test_custom_stats/t/001_custom_stats.pl
+++ b/src/test/modules/test_custom_stats/t/001_custom_stats.pl
@@ -164,10 +164,11 @@ $node->safe_psql('postgres', q(select test_custom_stats_fixed_reset()));
$node->safe_psql('postgres', q(select pg_stat_force_next_flush()));
my $anytime_test = q[
+ SET stats_flush_interval = '1s';
BEGIN;
-- Accumulate stats
select test_custom_stats_fixed_anytime_update() from generate_series(1, 2);
- -- Wait (has to be greater than PGSTAT_MIN_INTERVAL)
+ -- Wait (has to be greater than stats_flush_interval)
select pg_sleep(1.5);
-- Check
select 'anytime:'||numcalls from test_custom_stats_fixed_report();
@@ -183,11 +184,12 @@ like($result, qr/^anytime:2/m,
$node->safe_psql('postgres', q(select pg_stat_force_next_flush()));
$anytime_test = q[
+ SET stats_flush_interval = '1s';
BEGIN;
-- Accumulate stats
select test_custom_stats_var_anytime_update('entry2');
select test_custom_stats_var_anytime_update('entry2');
- -- Wait (has to be greater than PGSTAT_MIN_INTERVAL)
+ -- Wait (has to be greater than stats_flush_interval)
select pg_sleep(1.5);
-- Check
select * from test_custom_stats_var_report('entry2');
--
2.34.1
--C2xzVbxFmVrP7k6O
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="v7-0004-Remove-useless-calls-to-flush-some-stats.patch"
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