From: Álvaro Herrera <alvherre@kurilemu.de>
Date: Tue, 4 Nov 2025 19:31:43 +0000 (+0100)
Subject: Fix snapshot handling bug in recent BRIN fix
X-Git-Tag: REL_18_1~26
X-Git-Url: http://git.postgresql.org/gitweb/static/main.js?a=commitdiff_plain;h=8733f0b54c05239e059e473c46c1800dcd37cd40;p=postgresql.git

Fix snapshot handling bug in recent BRIN fix

Commit a95e3d84c0e0 added ActiveSnapshot push+pop when processing
work-items (BRIN autosummarization), but forgot to handle the case of
a transaction failing during the run, which drops the snapshot untimely.
Fix by making the pop conditional on an element being actually there.

Author: Álvaro Herrera <alvherre@kurilemu.de>
Backpatch-through: 13
Discussion: https://postgr.es/m/202511041648.nofajnuddmwk@alvherre.pgsql
---

diff --git a/src/backend/postmaster/autovacuum.c b/src/backend/postmaster/autovacuum.c
index 80d71eb1039..66620fb4755 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2544,7 +2544,8 @@ deleted:
 
 		PushActiveSnapshot(GetTransactionSnapshot());
 		perform_work_item(workitem);
-		PopActiveSnapshot();
+		if (ActiveSnapshotSet())	/* transaction could have aborted */
+			PopActiveSnapshot();
 
 		/*
 		 * Check for config changes before acquiring lock for further jobs.