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

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 208457584d975fe5d0697316ed4ec8397c19e85e..86a2e6bae6abdb5fdc62f1a2078f645111abc8a4 100644 (file)
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -7572,9 +7572,12 @@ heap_xlog_freeze_page(XLogReaderState *record)
        if (InHotStandby)
        {
                RelFileNode rnode;
+               TransactionId latestRemovedXid = cutoff_xid;
+
+               TransactionIdRetreat(latestRemovedXid);
 
                XLogRecGetBlockTag(record, 0, &rnode, NULL, NULL);
-               ResolveRecoveryConflictWithSnapshot(cutoff_xid, rnode);
+               ResolveRecoveryConflictWithSnapshot(latestRemovedXid, rnode);
        }
 
        if (XLogReadBufferForRedo(record, 0, &buffer) == BLK_NEEDS_REDO)