From c64a3a582201fc7d1925d374ad6fa5778b0d4d14 Mon Sep 17 00:00:00 2001 From: Bertrand Drouvot Date: Wed, 28 Jan 2026 07:53:13 +0000 Subject: [PATCH v5 2/4] Add GUC to specify non-transactional statistics flush interval 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/access/transam/xlog.c | 4 +-- src/backend/utils/activity/pgstat.c | 16 +++++++++- src/backend/utils/activity/pgstat_backend.c | 4 +-- src/backend/utils/activity/pgstat_io.c | 2 +- src/backend/utils/activity/pgstat_slru.c | 2 +- src/backend/utils/misc/guc_parameters.dat | 10 ++++++ src/backend/utils/misc/postgresql.conf.sample | 1 + src/include/pgstat.h | 1 + src/include/utils/guc_hooks.h | 1 + 10 files changed, 66 insertions(+), 7 deletions(-) 45.9% doc/src/sgml/ 6.5% src/backend/access/transam/ 31.8% src/backend/utils/activity/ 12.3% src/backend/utils/misc/ 3.2% src/include/ diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 5560b95ee60..3136816a933 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -8834,6 +8834,38 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv; + + stats_flush_interval (integer) + + stats_flush_interval configuration parameter + + + + + Sets the interval at which non-transactional statistics are made visible + during running transactions. Non-transactional statistics include, for + example, WAL activity and I/O operations. + They become visible at that interval in monitoring views such as + pg_stat_io + and pg_stat_wal + during running transactions. + If this value is specified without units, it is taken as milliseconds. + The default is 10 seconds (10s), which is probably + about the smallest value you would want in practice for long running + transactions. + + + + This parameter does not affect transactional statistics such as + pg_stat_all_tables columns (like + n_tup_ins, n_tup_upd, + n_tup_del), which are always flushed at transaction + boundaries to maintain consistency. + + + + + diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 9503aea5b4d..31523dea923 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -1087,7 +1087,7 @@ XLogInsertRecord(XLogRecData *rdata, /* Schedule next anytime stats update timeout */ 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); /* Required for the flush of pending stats WAL data */ pgstat_report_fixed = true; @@ -2073,7 +2073,7 @@ AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tli, bool opportunistic) /* Schedule next anytime stats update timeout */ if (IsUnderPostmaster && !get_timeout_active(ANYTIME_STATS_UPDATE_TIMEOUT)) enable_timeout_after(ANYTIME_STATS_UPDATE_TIMEOUT, - PGSTAT_MIN_INTERVAL); + pgstat_flush_interval); /* * Required for the flush of pending stats WAL data, per diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c index 2c9454677e9..dd174129403 100644 --- a/src/backend/utils/activity/pgstat.c +++ b/src/backend/utils/activity/pgstat.c @@ -203,6 +203,7 @@ 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; /* ---------- @@ -1304,7 +1305,7 @@ pgstat_prep_pending_entry(PgStat_Kind kind, Oid dboid, uint64 objid, bool *creat /* Schedule next anytime stats update timeout */ if (kind_info->flush_mode == FLUSH_ANYTIME && 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); } return entry_ref; @@ -2172,6 +2173,19 @@ 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/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c index 9dcb24db975..f5b8c7b039c 100644 --- a/src/backend/utils/activity/pgstat_backend.c +++ b/src/backend/utils/activity/pgstat_backend.c @@ -69,7 +69,7 @@ pgstat_count_backend_io_op_time(IOObject io_object, IOContext io_context, /* Schedule next anytime stats update timeout */ 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); backend_has_iostats = true; pgstat_report_fixed = true; @@ -89,7 +89,7 @@ pgstat_count_backend_io_op(IOObject io_object, IOContext io_context, /* Schedule next anytime stats update timeout */ 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); backend_has_iostats = true; pgstat_report_fixed = true; diff --git a/src/backend/utils/activity/pgstat_io.c b/src/backend/utils/activity/pgstat_io.c index 53dbf2a514b..b69a1e26f7d 100644 --- a/src/backend/utils/activity/pgstat_io.c +++ b/src/backend/utils/activity/pgstat_io.c @@ -82,7 +82,7 @@ pgstat_count_io_op(IOObject io_object, IOContext io_context, IOOp io_op, /* Schedule next anytime stats update timeout */ 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); have_iostats = true; pgstat_report_fixed = true; diff --git a/src/backend/utils/activity/pgstat_slru.c b/src/backend/utils/activity/pgstat_slru.c index 1d16cde1889..36231ee874b 100644 --- a/src/backend/utils/activity/pgstat_slru.c +++ b/src/backend/utils/activity/pgstat_slru.c @@ -226,7 +226,7 @@ get_slru_entry(int slru_idx) /* Schedule next anytime stats update timeout */ 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); have_slrustats = true; pgstat_report_fixed = true; diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat index f0260e6e412..3bb43362e51 100644 --- a/src/backend/utils/misc/guc_parameters.dat +++ b/src/backend/utils/misc/guc_parameters.dat @@ -2782,6 +2782,16 @@ 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 c4f92fcdac8..6ce5a250170 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -669,6 +669,7 @@ #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 1651f16f966..e0f222695bf 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -816,6 +816,7 @@ 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 b6ecb0e769f..3a2ae6c41cd 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, -- 2.34.1