From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed, 21 Apr 2021 22:36:12 +0000 (-0400)
Subject: Add comment about extract_autovac_opts not holding lock
X-Git-Tag: REL_14_BETA1~168
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=7c298c6573a0f181963ddcb40c850fa9c7da0ada;p=thirdparty%2Fpostgresql.git

Add comment about extract_autovac_opts not holding lock

Per observation from Tom Lane.

Discussion: https://postgr.es/m/1901125.1617904665@sss.pgh.pa.us
---

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 83c584ddc8c..d516df0ac5c 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2783,6 +2783,11 @@ deleted2:
  *
  * Given a relation's pg_class tuple, return the AutoVacOpts portion of
  * reloptions, if set; otherwise, return NULL.
+ *
+ * Note: callers do not have a relation lock on the table at this point,
+ * so the table could have been dropped, and its catalog rows gone, after
+ * we acquired the pg_class row.  If pg_class had a TOAST table, this would
+ * be a risk; fortunately, it doesn't.
  */
 static AutoVacOpts *
 extract_autovac_opts(HeapTuple tup, TupleDesc pg_class_desc)