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| author | Michael Paquier <michael@paquier.xyz> | 2019-03-31 22:59:12 +0900 |
|---|---|---|
| committer | Michael Paquier <michael@paquier.xyz> | 2019-03-31 22:59:12 +0900 |
| commit | 2aa6e331ead7f3ad080561495ad4bd3bc7cd8913 (patch) | |
| tree | 8bcde6475ded6ccd0eb393c2bdbe2f98177a10c3 | |
| parent | 47b3c26642e6850e8dfa7afe01db78320b11549e (diff) | |
| download | postgresql-2aa6e331ead7f3ad080561495ad4bd3bc7cd8913.tar.gz postgresql-2aa6e331ead7f3ad080561495ad4bd3bc7cd8913.zip | |
Skip redundant anti-wraparound vacuums
An anti-wraparound vacuum has to be by definition aggressive as it needs
to work on all the pages of a relation. However it can happen that due
to some concurrent activity an anti-wraparound vacuum is marked as
non-aggressive, which makes it redundant with a previous run, and
it is actually useless as an anti-wraparound vacuum should process all
the pages of a relation. This commit makes such vacuums to be skipped.
An anti-wraparound vacuum not aggressive can be found easily by mixing
low values of autovacuum_freeze_max_age (to control anti-wraparound) and
autovacuum_freeze_table_age (to control the aggressiveness).
28a8fa9 has added some extra logging printing all the possible
combinations of anti-wraparound and aggressive vacuums, which now gets
simplified as an anti-wraparound vacuum also non-aggressive gets
skipped.
Per discussion mainly between Andrew Dunstan, Robert Haas, Álvaro
Herrera, Kyotaro Horiguchi, Masahiko Sawada, and myself.
Author: Kyotaro Horiguchi, Michael Paquier
Reviewed-by: Andrew Dunstan, Álvaro Herrera
Discussion: https://postgr.es/m/20180914153554.562muwr3uwujno75@alvherre.pgsql
| -rw-r--r-- | src/backend/access/heap/vacuumlazy.c | 24 |
1 files changed, 20 insertions, 4 deletions
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c index 5c554f94659..b5b464e4a9d 100644 --- a/src/backend/access/heap/vacuumlazy.c +++ b/src/backend/access/heap/vacuumlazy.c @@ -248,6 +248,23 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params, if (params->options & VACOPT_DISABLE_PAGE_SKIPPING) aggressive = true; + /* + * Normally the relfrozenxid for an anti-wraparound vacuum will be old + * enough to force an aggressive vacuum. However, a concurrent vacuum + * might have already done this work that the relfrozenxid in relcache has + * been updated. If that happens this vacuum is redundant, so skip it. + */ + if (params->is_wraparound && !aggressive) + { + ereport(DEBUG1, + (errmsg("skipping redundant vacuum to prevent wraparound of table \"%s.%s.%s\"", + get_database_name(MyDatabaseId), + get_namespace_name(RelationGetNamespace(onerel)), + RelationGetRelationName(onerel)))); + pgstat_progress_end_command(); + return; + } + vacrelstats = (LVRelStats *) palloc0(sizeof(LVRelStats)); vacrelstats->old_rel_pages = onerel->rd_rel->relpages; @@ -375,10 +392,9 @@ heap_vacuum_rel(Relation onerel, VacuumParams *params, initStringInfo(&buf); if (params->is_wraparound) { - if (aggressive) - msgfmt = _("automatic aggressive vacuum to prevent wraparound of table \"%s.%s.%s\": index scans: %d\n"); - else - msgfmt = _("automatic vacuum to prevent wraparound of table \"%s.%s.%s\": index scans: %d\n"); + /* an anti-wraparound vacuum has to be aggressive */ + Assert(aggressive); + msgfmt = _("automatic aggressive vacuum to prevent wraparound of table \"%s.%s.%s\": index scans: %d\n"); } else { |