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Fix stats_fetch_consistency with stats for fixed-numbered objects

author Michael Paquier <michael@paquier.xyz>

Thu, 1 Feb 2024 08:12:50 +0000 (17:12 +0900)

committer Michael Paquier <michael@paquier.xyz>

Thu, 1 Feb 2024 08:12:50 +0000 (17:12 +0900)

This impacts the statistics retrieved in transactions for the following
views when updating the value of stats_fetch_consistency, leading to
behaviors contrary to what is documented since 605994651b6a as an update
of this parameter should discard all statistics snapshot data:
- pg_stat_archiver
- pg_stat_bgwriter
- pg_stat_checkpointer
- pg_stat_io
- pg_stat_slru
- pg_stat_wal

For example, updating stats_fetch_consistency from "snapshot" to "cache"
in a transaction did not re-fetch any fresh data, using data cached from
the time when "snapshot" was in use.

Author: Shinya Kato
Discussion: https://postgr.es/m/d77fc5190d4dbe1738d77231488e768b@oss.nttdata.com
Backpatch-through: 15

src/backend/utils/activity/pgstat.c patch | blob | blame | history

diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c

index 125ca97b186f4cbe0786b1c8d8c4593bb3f6e3fc..9bfc7a951857371caf92664ced8be955c782e039 100644 (file)

--- a/src/backend/utils/activity/pgstat.c

+++ b/src/backend/utils/activity/pgstat.c

@@ -943,6 +943,9 @@ pgstat_snapshot_fixed(PgStat_Kind kind)

Assert(pgstat_is_kind_valid(kind));

Assert(pgstat_get_kind_info(kind)->fixed_amount);

+ if (force_stats_snapshot_clear)

+ pgstat_clear_snapshot();

if (pgstat_fetch_consistency == PGSTAT_FETCH_CONSISTENCY_SNAPSHOT)

pgstat_build_snapshot();

else

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