From 892a0e4e4559fc200d4803db24f4babca37fe76d Mon Sep 17 00:00:00 2001
From: Simon Riggs <simon@2ndQuadrant.com>
Date: Sat, 27 Jun 2015 00:46:58 +0100
Subject: [PATCH] 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.

Backpatch to all versions 9.0+

Analysis and report by Marco Nenciarini

Bug fix by Simon Riggs
---
 src/backend/access/heap/heapam.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 9918c226c28..b068483c58e 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -7064,7 +7064,13 @@ heap_xlog_freeze_page(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, rnode);
+	}
 
 	/* If we have a full-page image, restore it and we're done */
 	if (record->xl_info & XLR_BKP_BLOCK(0))