From 3f1db99bfabbb9d4afc41f362d9801512f4c7c65 Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Mon, 3 Mar 2025 09:57:48 +0900 Subject: [PATCH] Handle auxiliary processes in SQL functions of backend statistics This commit impacts the following SQL functions, authorizing the access to the PGPROC entries of auxiliary processes when attempting to fetch or reset backend-level pgstats entries: - pg_stat_reset_backend_stats() - pg_stat_get_backend_io() This is relevant since a051e71e28a1 for at least the WAL summarizer, WAL receiver and WAL writer processes, that has changed the backend statistics to authorize these three following the addition of WAL I/O statistics in pg_stat_io and backend statistics. The code is more flexible with future changes written this way, adapting automatically to any updates done in pgstat_tracks_backend_bktype(). While on it, pgstat_report_wal() gains a call to pgstat_flush_backend(), making sure that backend I/O statistics are updated when calling this routine. This makes the statistics report correctly for the WAL writer. WAL receiver and WAL summarizer do not call pgstat_report_wal() yet (spoiler: both should). It should be possible to lift some of the existing restrictions for other auxiliary processes, as well, but this is left as future work. Reported-by: Rahila Syed Author: Bertrand Drouvot Discussion: https://postgr.es/m/CAH2L28v9BwN8_y0k6FQ591=0g2Hj_esHLGj3bP38c9nmVykoiA@mail.gmail.com --- src/backend/utils/activity/pgstat_backend.c | 17 +++++++-------- src/backend/utils/activity/pgstat_wal.c | 1 + src/backend/utils/adt/pgstatfuncs.c | 23 +++++++++++++++------ 3 files changed, 26 insertions(+), 15 deletions(-) diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c index 3c9ebbcd69c..a9343b7b59e 100644 --- a/src/backend/utils/activity/pgstat_backend.c +++ b/src/backend/utils/activity/pgstat_backend.c @@ -103,11 +103,10 @@ pgstat_fetch_stat_backend_by_pid(int pid, BackendType *bktype) if (bktype) *bktype = B_INVALID; - /* - * This could be an auxiliary process but these do not report backend - * statistics due to pgstat_tracks_backend_bktype(), so there is no need - * for an extra call to AuxiliaryPidGetProc(). - */ + /* this could be an auxiliary process */ + if (!proc) + proc = AuxiliaryPidGetProc(pid); + if (!proc) return NULL; @@ -117,6 +116,10 @@ pgstat_fetch_stat_backend_by_pid(int pid, BackendType *bktype) if (!beentry) return NULL; + /* check if the backend type tracks statistics */ + if (!pgstat_tracks_backend_bktype(beentry->st_backendType)) + return NULL; + backend_stats = pgstat_fetch_stat_backend(procNumber); if (!backend_stats) return NULL; @@ -125,10 +128,6 @@ pgstat_fetch_stat_backend_by_pid(int pid, BackendType *bktype) if (beentry->st_procpid != pid) return NULL; - /* backend may be gone, so recheck in case */ - if (beentry->st_backendType == B_INVALID) - return NULL; - if (bktype) *bktype = beentry->st_backendType; diff --git a/src/backend/utils/activity/pgstat_wal.c b/src/backend/utils/activity/pgstat_wal.c index 943be0cbeef..5d3da4b674e 100644 --- a/src/backend/utils/activity/pgstat_wal.c +++ b/src/backend/utils/activity/pgstat_wal.c @@ -55,6 +55,7 @@ pgstat_report_wal(bool force) /* flush IO stats */ pgstat_flush_io(nowait); + (void) pgstat_flush_backend(nowait, PGSTAT_BACKEND_FLUSH_IO); } /* diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c index 68830db8633..0212d8d5906 100644 --- a/src/backend/utils/adt/pgstatfuncs.c +++ b/src/backend/utils/adt/pgstatfuncs.c @@ -1919,19 +1919,30 @@ Datum pg_stat_reset_backend_stats(PG_FUNCTION_ARGS) { PGPROC *proc; + PgBackendStatus *beentry; + ProcNumber procNumber; int backend_pid = PG_GETARG_INT32(0); proc = BackendPidGetProc(backend_pid); - /* - * This could be an auxiliary process but these do not report backend - * statistics due to pgstat_tracks_backend_bktype(), so there is no need - * for an extra call to AuxiliaryPidGetProc(). - */ + /* This could be an auxiliary process */ + if (!proc) + proc = AuxiliaryPidGetProc(backend_pid); + if (!proc) PG_RETURN_VOID(); - pgstat_reset(PGSTAT_KIND_BACKEND, InvalidOid, GetNumberFromPGProc(proc)); + procNumber = GetNumberFromPGProc(proc); + + beentry = pgstat_get_beentry_by_proc_number(procNumber); + if (!beentry) + PG_RETURN_VOID(); + + /* Check if the backend type tracks statistics */ + if (!pgstat_tracks_backend_bktype(beentry->st_backendType)) + PG_RETURN_VOID(); + + pgstat_reset(PGSTAT_KIND_BACKEND, InvalidOid, procNumber); PG_RETURN_VOID(); }