Allocate access strategy in parallel VACUUM workers.

Amit Kapila · Amit Kapila · commit 48d4a8c88ba7 · 2021-04-12T09:03:16.000+05:30
Currently, parallel vacuum workers don't use any buffer access strategy. We can fix it either by propagating the access strategy from a leader or allow each worker to use BAS_VACUUM access strategy type. We don't see much use in propagating this information from leader as both leader and workers are supposed to use the same strategy. We might want to use a different access strategy for leader and workers but that would be a separate optimization not suitable for back-branches. This has been fixed in HEAD as commit f6b8f19. Author: Amit Kapila Reviewed-by: Sawada Masahiko, Bharath Rupireddy Discussion: https://postgr.es/m/CAA4eK1KbmJgRV2W3BbzRnKUSrukN7SbqBBriC4RDB5KBhopkGQ@mail.gmail.com
diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
@@ -3510,6 +3510,9 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
 	vac_open_indexes(onerel, RowExclusiveLock, &nindexes, &indrels);
 	Assert(nindexes > 0);
 
+	/* Each parallel VACUUM worker gets its own access strategy */
+	vac_strategy = GetAccessStrategy(BAS_VACUUM);
+
 	/* Set dead tuple space */
 	dead_tuples = (LVDeadTuples *) shm_toc_lookup(toc,
 												  PARALLEL_VACUUM_KEY_DEAD_TUPLES,
@@ -3564,6 +3567,7 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
 
 	vac_close_indexes(nindexes, indrels, RowExclusiveLock);
 	table_close(onerel, ShareUpdateExclusiveLock);
+	FreeAccessStrategy(vac_strategy);
 	pfree(stats);
 }
 
