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-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=ef81697fee774d3e21e0c479f3f9515a7d0f256f;p=thirdparty%2Fpostgresql.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 2d10ee22377..183319c4b1c 100644
--- a/src/backend/postmaster/autovacuum.c
+++ b/src/backend/postmaster/autovacuum.c
@@ -2598,7 +2598,8 @@ 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.