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Fix stale comment in parallel_vacuum_main().

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The comment claimed that a parallel vacuum worker has only the
PROC_IN_VACUUM flag because parallel vacuum is not supported for
autovacuum, but commit 1ff3180ca0 allowed autovacuum to use parallel
vacuum workers.

The assertion itself still holds: the leader, whether a backend
running VACUUM or an autovacuum worker, sets PROC_IN_VACUUM before
taking its snapshot, and a parallel worker inherits the flag when
importing the leader's snapshot. The leader's other flags don't reach
the worker, since the snapshot import copies only the PROC_XMIN_FLAGS
bits and PROC_IS_AUTOVACUUM is never set on parallel workers, which
run as regular background workers. Reword the comment to explain that.

Oversight in commit 1ff3180ca0.

Author: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CALj2ACVwQ4WABqq8Lnf+VZEJ45jcTFhyFLFr_ctfS4=QLL-r5w@mail.gmail.com
Backpatch-through: 19
This commit is contained in:
Masahiko Sawada
2026-07-29 09:52:10 -07:00
parent bef46aed39
commit 4ee0ccfd55
1 changed files with 10 additions and 2 deletions
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12
src/backend/commands/vacuumparallel.c
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@@ -1209,8 +1209,16 @@ parallel_vacuum_main(dsm_segment *seg, shm_toc *toc)
ErrorContextCallback errcallback;
/*
* A parallel vacuum worker must have only PROC_IN_VACUUM flag since we
* don't support parallel vacuum for autovacuum as of now.
* A parallel vacuum worker carries only the PROC_IN_VACUUM flag. The
* leader, whether it's a backend running a VACUUM command or an
* autovacuum worker, sets PROC_IN_VACUUM when it starts vacuuming the
* table, and the worker inherits the flag by importing the leader's
* snapshot (see ProcArrayInstallRestoredXmin). The leader's other flags
* don't reach the worker: the snapshot import copies only the
* PROC_XMIN_FLAGS bits, so PROC_VACUUM_FOR_WRAPAROUND isn't carried
* over, and PROC_IS_AUTOVACUUM is never set on the worker in the first
* place since parallel workers run as regular background workers, not
* autovacuum workers.
*/
Assert(MyProc->statusFlags == PROC_IN_VACUUM);