Attached patch fixes a bug reported privately by Stephen this morning.
He complained about deadlocking ON CONFLICT DO NOTHING statements.
There were no exclusion constraints involved, and yet they were
incorrectly indicated as being involved in log messages that related
to these deadlocks.

Peter Geoghegan
From bc481af77994057cb1ffe4a0e471b38bb00dc228 Mon Sep 17 00:00:00 2001
From: Peter Geoghegan <>
Date: Mon, 7 Mar 2016 13:16:24 -0800
Subject: [PATCH] Avoid incorrectly indicating exclusion constraint wait

INSERT ... ON CONFLICT's precheck may have to wait on the outcome of
another insertion, which may or may not itself be a speculative
insertion.  This wait is not necessarily associated with an exclusion
constraint, but was always reported that way in log messages if the wait
happened to involve a tuple that had no speculative token.

Bug reported privately by Stephen Frost.  His case involved ON CONFLICT
DO NOTHING, where spurious references to exclusion constraints in log
messages were more likely.
 src/backend/executor/execIndexing.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/backend/executor/execIndexing.c b/src/backend/executor/execIndexing.c
index 838cee7..5d553d5 100644
--- a/src/backend/executor/execIndexing.c
+++ b/src/backend/executor/execIndexing.c
@@ -725,6 +725,7 @@ retry:
 		TransactionId xwait;
 		ItemPointerData ctid_wait;
+		XLTW_Oper		reason_wait;
 		Datum		existing_values[INDEX_MAX_KEYS];
 		bool		existing_isnull[INDEX_MAX_KEYS];
 		char	   *error_new;
@@ -783,13 +784,14 @@ retry:
 			  TransactionIdPrecedes(GetCurrentTransactionId(), xwait))))
 			ctid_wait = tup->t_data->t_ctid;
+			reason_wait = indexInfo->ii_ExclusionOps ?
+				XLTW_RecheckExclusionConstr : XLTW_InsertIndex;
 			if (DirtySnapshot.speculativeToken)
-				XactLockTableWait(xwait, heap, &ctid_wait,
-								  XLTW_RecheckExclusionConstr);
+				XactLockTableWait(xwait, heap, &ctid_wait, reason_wait);
 			goto retry;

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