From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed, 25 May 2016 23:39:49 +0000 (-0400)
Subject: Avoid hot standby cancels from VAC FREEZE
X-Git-Tag: REL9_2_18~52
X-Git-Url: http://git.postgresql.org/gitweb/?a=commitdiff_plain;h=294509ea9bb3305230659fd76bd355aec6fcd039;p=postgresql.git

Avoid hot standby cancels from VAC FREEZE

VACUUM FREEZE generated false cancelations of standby queries on an
otherwise idle master. Caused by an off-by-one error on cutoff_xid
which goes back to original commit.

Analysis and report by Marco Nenciarini

Bug fix by Simon Riggs

This is a correct backpatch of commit 66fbcb0d2e to branches 9.1 through
9.4.  That commit was backpatched to 9.0 originally, but it was
immediately reverted in 9.0-9.4 because it didn't compile.
---

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index eb8eada27d6..434880ac295 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -4764,7 +4764,13 @@ heap_xlog_freeze(XLogRecPtr lsn, XLogRecord *record)
 	 * consider the frozen xids as running.
 	 */
 	if (InHotStandby)
-		ResolveRecoveryConflictWithSnapshot(cutoff_xid, xlrec->node);
+	{
+		TransactionId latestRemovedXid = cutoff_xid;
+
+		TransactionIdRetreat(latestRemovedXid);
+
+		ResolveRecoveryConflictWithSnapshot(latestRemovedXid, xlrec->node);
+	}
 
 	/* If we have a full-page image, restore it and we're done */
 	if (record->xl_info & XLR_BKP_BLOCK(0))