From e518fa7adfc28e0d0a99fe4e5711386d9a5c6532 Mon Sep 17 00:00:00 2001
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
Date: Wed, 27 Nov 2013 17:45:25 -0300
Subject: [PATCH] Cope with heap_fetch failure while locking an update chain

The reason for the fetch failure is that the tuple was removed because
it was dead; so the failure is innocuous and can be ignored.  Moreover,
there's no need for further work and we can return success to the caller
immediately.  EvalPlanQualFetch is doing something very similar to this
already.

Report and test case from Andres Freund in
20131124000203.GA4403@alap2.anarazel.de
---
 src/backend/access/heap/heapam.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index a21f31b4095..f55e612590f 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -4824,7 +4824,16 @@ heap_lock_updated_tuple_rec(Relation rel, ItemPointer tid, TransactionId xid,
 		ItemPointerCopy(&tupid, &(mytup.t_self));
 
 		if (!heap_fetch(rel, SnapshotAny, &mytup, &buf, false, NULL))
-			elog(ERROR, "unable to fetch updated version of tuple");
+		{
+			/*
+			 * if we fail to find the updated version of the tuple, it's
+			 * because it was vacuumed/pruned away after its creator
+			 * transaction aborted.  So behave as if we got to the end of the
+			 * chain, and there's no further tuple to lock: return success to
+			 * caller.
+			 */
+			return HeapTupleMayBeUpdated;
+		}
 
 l4:
 		CHECK_FOR_INTERRUPTS();
-- 
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