fix-merge-bug-17.patch

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
new file mode 100644
index ea5cc10..ad28abe
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -79,6 +79,7 @@ static bool GetTupleForTrigger(EState *e
 							   ItemPointer tid,
 							   LockTupleMode lockmode,
 							   TupleTableSlot *oldslot,
+							   bool do_epq_recheck,
 							   TupleTableSlot **epqslot,
 							   TM_Result *tmresultp,
 							   TM_FailureData *tmfdp);
@@ -2679,13 +2680,14 @@ ExecASDeleteTriggers(EState *estate, Res
  * back the concurrently updated tuple if any.
  */
 bool
-ExecBRDeleteTriggers(EState *estate, EPQState *epqstate,
-					 ResultRelInfo *relinfo,
-					 ItemPointer tupleid,
-					 HeapTuple fdw_trigtuple,
-					 TupleTableSlot **epqslot,
-					 TM_Result *tmresult,
-					 TM_FailureData *tmfd)
+ExecBRDeleteTriggersNew(EState *estate, EPQState *epqstate,
+						ResultRelInfo *relinfo,
+						ItemPointer tupleid,
+						HeapTuple fdw_trigtuple,
+						TupleTableSlot **epqslot,
+						TM_Result *tmresult,
+						TM_FailureData *tmfd,
+						bool is_merge_delete)
 {
 	TupleTableSlot *slot = ExecGetTriggerOldSlot(estate, relinfo);
 	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
@@ -2700,9 +2702,17 @@ ExecBRDeleteTriggers(EState *estate, EPQ
 	{
 		TupleTableSlot *epqslot_candidate = NULL;
 
+		/*
+		 * Get a copy of the on-disk tuple we are planning to delete.  In
+		 * general, if the tuple has been concurrently updated, we should
+		 * recheck it using EPQ.  However, if this is a MERGE DELETE action,
+		 * we skip this EPQ recheck and leave it to the caller (it must do
+		 * additional rechecking, and might end up executing a different
+		 * action entirely).
+		 */
 		if (!GetTupleForTrigger(estate, epqstate, relinfo, tupleid,
-								LockTupleExclusive, slot, &epqslot_candidate,
-								tmresult, tmfd))
+								LockTupleExclusive, slot, !is_merge_delete,
+								&epqslot_candidate, tmresult, tmfd))
 			return false;
 
 		/*
@@ -2766,6 +2776,24 @@ ExecBRDeleteTriggers(EState *estate, EPQ
 }
 
 /*
+ * ABI-compatible wrapper to emulate old version of the above function.
+ * Do not call this version in new code.
+ */
+bool
+ExecBRDeleteTriggers(EState *estate, EPQState *epqstate,
+					 ResultRelInfo *relinfo,
+					 ItemPointer tupleid,
+					 HeapTuple fdw_trigtuple,
+					 TupleTableSlot **epqslot,
+					 TM_Result *tmresult,
+					 TM_FailureData *tmfd)
+{
+	return ExecBRDeleteTriggersNew(estate, epqstate, relinfo, tupleid,
+								   fdw_trigtuple, epqslot, tmresult, tmfd,
+								   false);
+}
+
+/*
  * Note: is_crosspart_update must be true if the DELETE is being performed
  * as part of a cross-partition update.
  */
@@ -2792,6 +2820,7 @@ ExecARDeleteTriggers(EState *estate,
 							   tupleid,
 							   LockTupleExclusive,
 							   slot,
+							   false,
 							   NULL,
 							   NULL,
 							   NULL);
@@ -2930,13 +2959,14 @@ ExecASUpdateTriggers(EState *estate, Res
 }
 
 bool
-ExecBRUpdateTriggers(EState *estate, EPQState *epqstate,
-					 ResultRelInfo *relinfo,
-					 ItemPointer tupleid,
-					 HeapTuple fdw_trigtuple,
-					 TupleTableSlot *newslot,
-					 TM_Result *tmresult,
-					 TM_FailureData *tmfd)
+ExecBRUpdateTriggersNew(EState *estate, EPQState *epqstate,
+						ResultRelInfo *relinfo,
+						ItemPointer tupleid,
+						HeapTuple fdw_trigtuple,
+						TupleTableSlot *newslot,
+						TM_Result *tmresult,
+						TM_FailureData *tmfd,
+						bool is_merge_update)
 {
 	TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
 	TupleTableSlot *oldslot = ExecGetTriggerOldSlot(estate, relinfo);
@@ -2957,10 +2987,17 @@ ExecBRUpdateTriggers(EState *estate, EPQ
 	{
 		TupleTableSlot *epqslot_candidate = NULL;
 
-		/* get a copy of the on-disk tuple we are planning to update */
+		/*
+		 * Get a copy of the on-disk tuple we are planning to update.  In
+		 * general, if the tuple has been concurrently updated, we should
+		 * recheck it using EPQ.  However, if this is a MERGE UPDATE action,
+		 * we skip this EPQ recheck and leave it to the caller (it must do
+		 * additional rechecking, and might end up executing a different
+		 * action entirely).
+		 */
 		if (!GetTupleForTrigger(estate, epqstate, relinfo, tupleid,
-								lockmode, oldslot, &epqslot_candidate,
-								tmresult, tmfd))
+								lockmode, oldslot, !is_merge_update,
+								&epqslot_candidate, tmresult, tmfd))
 			return false;		/* cancel the update action */
 
 		/*
@@ -3083,6 +3120,24 @@ ExecBRUpdateTriggers(EState *estate, EPQ
 }
 
 /*
+ * ABI-compatible wrapper to emulate old version of the above function.
+ * Do not call this version in new code.
+ */
+bool
+ExecBRUpdateTriggers(EState *estate, EPQState *epqstate,
+					 ResultRelInfo *relinfo,
+					 ItemPointer tupleid,
+					 HeapTuple fdw_trigtuple,
+					 TupleTableSlot *newslot,
+					 TM_Result *tmresult,
+					 TM_FailureData *tmfd)
+{
+	return ExecBRUpdateTriggersNew(estate, epqstate, relinfo, tupleid,
+								   fdw_trigtuple, newslot, tmresult, tmfd,
+								   false);
+}
+
+/*
  * Note: 'src_partinfo' and 'dst_partinfo', when non-NULL, refer to the source
  * and destination partitions, respectively, of a cross-partition update of
  * the root partitioned table mentioned in the query, given by 'relinfo'.
@@ -3132,6 +3187,7 @@ ExecARUpdateTriggers(EState *estate, Res
 							   tupleid,
 							   LockTupleExclusive,
 							   oldslot,
+							   false,
 							   NULL,
 							   NULL,
 							   NULL);
@@ -3288,6 +3344,7 @@ GetTupleForTrigger(EState *estate,
 				   ItemPointer tid,
 				   LockTupleMode lockmode,
 				   TupleTableSlot *oldslot,
+				   bool do_epq_recheck,
 				   TupleTableSlot **epqslot,
 				   TM_Result *tmresultp,
 				   TM_FailureData *tmfdp)
@@ -3347,29 +3404,30 @@ GetTupleForTrigger(EState *estate,
 				if (tmfd.traversed)
 				{
 					/*
-					 * Recheck the tuple using EPQ. For MERGE, we leave this
-					 * to the caller (it must do additional rechecking, and
-					 * might end up executing a different action entirely).
+					 * Recheck the tuple using EPQ, if requested.  Otherwise,
+					 * just return that it was concurrently updated.
 					 */
-					if (estate->es_plannedstmt->commandType == CMD_MERGE)
+					if (do_epq_recheck)
 					{
-						if (tmresultp)
-							*tmresultp = TM_Updated;
-						return false;
-					}
-
-					*epqslot = EvalPlanQual(epqstate,
-											relation,
-											relinfo->ri_RangeTableIndex,
-											oldslot);
+						*epqslot = EvalPlanQual(epqstate,
+												relation,
+												relinfo->ri_RangeTableIndex,
+												oldslot);
 
-					/*
-					 * If PlanQual failed for updated tuple - we must not
-					 * process this tuple!
-					 */
-					if (TupIsNull(*epqslot))
+						/*
+						 * If PlanQual failed for updated tuple - we must not
+						 * process this tuple!
+						 */
+						if (TupIsNull(*epqslot))
+						{
+							*epqslot = NULL;
+							return false;
+						}
+					}
+					else
 					{
-						*epqslot = NULL;
+						if (tmresultp)
+							*tmresultp = TM_Updated;
 						return false;
 					}
 				}
diff --git a/src/backend/executor/nodeModifyTable.c b/src/backend/executor/nodeModifyTable.c
new file mode 100644
index a0d1091..c230b66
--- a/src/backend/executor/nodeModifyTable.c
+++ b/src/backend/executor/nodeModifyTable.c
@@ -1349,9 +1349,10 @@ ExecDeletePrologue(ModifyTableContext *c
 		if (context->estate->es_insert_pending_result_relations != NIL)
 			ExecPendingInserts(context->estate);
 
-		return ExecBRDeleteTriggers(context->estate, context->epqstate,
-									resultRelInfo, tupleid, oldtuple,
-									epqreturnslot, result, &context->tmfd);
+		return ExecBRDeleteTriggersNew(context->estate, context->epqstate,
+									   resultRelInfo, tupleid, oldtuple,
+									   epqreturnslot, result, &context->tmfd,
+									   context->mtstate->operation == CMD_MERGE);
 	}
 
 	return true;
@@ -1947,9 +1948,10 @@ ExecUpdatePrologue(ModifyTableContext *c
 		if (context->estate->es_insert_pending_result_relations != NIL)
 			ExecPendingInserts(context->estate);
 
-		return ExecBRUpdateTriggers(context->estate, context->epqstate,
-									resultRelInfo, tupleid, oldtuple, slot,
-									result, &context->tmfd);
+		return ExecBRUpdateTriggersNew(context->estate, context->epqstate,
+									   resultRelInfo, tupleid, oldtuple, slot,
+									   result, &context->tmfd,
+									   context->mtstate->operation == CMD_MERGE);
 	}
 
 	return true;
diff --git a/src/include/commands/trigger.h b/src/include/commands/trigger.h
new file mode 100644
index 8a5a9fe..f9e4dc4
--- a/src/include/commands/trigger.h
+++ b/src/include/commands/trigger.h
@@ -206,6 +206,15 @@ extern void ExecBSDeleteTriggers(EState
 extern void ExecASDeleteTriggers(EState *estate,
 								 ResultRelInfo *relinfo,
 								 TransitionCaptureState *transition_capture);
+extern bool ExecBRDeleteTriggersNew(EState *estate,
+									EPQState *epqstate,
+									ResultRelInfo *relinfo,
+									ItemPointer tupleid,
+									HeapTuple fdw_trigtuple,
+									TupleTableSlot **epqslot,
+									TM_Result *tmresult,
+									TM_FailureData *tmfd,
+									bool is_merge_delete);
 extern bool ExecBRDeleteTriggers(EState *estate,
 								 EPQState *epqstate,
 								 ResultRelInfo *relinfo,
@@ -228,6 +237,15 @@ extern void ExecBSUpdateTriggers(EState
 extern void ExecASUpdateTriggers(EState *estate,
 								 ResultRelInfo *relinfo,
 								 TransitionCaptureState *transition_capture);
+extern bool ExecBRUpdateTriggersNew(EState *estate,
+									EPQState *epqstate,
+									ResultRelInfo *relinfo,
+									ItemPointer tupleid,
+									HeapTuple fdw_trigtuple,
+									TupleTableSlot *newslot,
+									TM_Result *tmresult,
+									TM_FailureData *tmfd,
+									bool is_merge_update);
 extern bool ExecBRUpdateTriggers(EState *estate,
 								 EPQState *epqstate,
 								 ResultRelInfo *relinfo,
diff --git a/src/test/isolation/expected/merge-match-recheck.out b/src/test/isolation/expected/merge-match-recheck.out
new file mode 100644
index 9a44a59..90300f1
--- a/src/test/isolation/expected/merge-match-recheck.out
+++ b/src/test/isolation/expected/merge-match-recheck.out
@@ -241,19 +241,28 @@ starting permutation: update_bal1_tg mer
 s2: NOTICE:  Update: (1,160,s1,setup) -> (1,50,s1,"setup updated by update_bal1_tg")
 step update_bal1_tg: UPDATE target_tg t SET balance = 50, val = t.val || ' updated by update_bal1_tg' WHERE t.key = 1;
 step merge_bal_tg: 
-  MERGE INTO target_tg t
-  USING (SELECT 1 as key) s
-  ON s.key = t.key
-  WHEN MATCHED AND balance < 100 THEN
-	UPDATE SET balance = balance * 2, val = t.val || ' when1'
-  WHEN MATCHED AND balance < 200 THEN
-	UPDATE SET balance = balance * 4, val = t.val || ' when2'
-  WHEN MATCHED AND balance < 300 THEN
-	UPDATE SET balance = balance * 8, val = t.val || ' when3';
+  WITH t AS (
+    MERGE INTO target_tg t
+    USING (SELECT 1 as key) s
+    ON s.key = t.key
+    WHEN MATCHED AND balance < 100 THEN
+      UPDATE SET balance = balance * 2, val = t.val || ' when1'
+    WHEN MATCHED AND balance < 200 THEN
+      UPDATE SET balance = balance * 4, val = t.val || ' when2'
+    WHEN MATCHED AND balance < 300 THEN
+      UPDATE SET balance = balance * 8, val = t.val || ' when3'
+    RETURNING t.*
+  )
+  SELECT * FROM t;
  <waiting ...>
 step c2: COMMIT;
 s1: NOTICE:  Update: (1,50,s1,"setup updated by update_bal1_tg") -> (1,100,s1,"setup updated by update_bal1_tg when1")
 step merge_bal_tg: <... completed>
+key|balance|status|val                                  
+---+-------+------+-------------------------------------
+  1|    100|s1    |setup updated by update_bal1_tg when1
+(1 row)
+
 step select1_tg: SELECT * FROM target_tg;
 key|balance|status|val                                  
 ---+-------+------+-------------------------------------
diff --git a/src/test/isolation/specs/merge-match-recheck.spec b/src/test/isolation/specs/merge-match-recheck.spec
new file mode 100644
index 298b2bf..22688bb
--- a/src/test/isolation/specs/merge-match-recheck.spec
+++ b/src/test/isolation/specs/merge-match-recheck.spec
@@ -99,15 +99,19 @@ step "merge_bal_pa"
 }
 step "merge_bal_tg"
 {
-  MERGE INTO target_tg t
-  USING (SELECT 1 as key) s
-  ON s.key = t.key
-  WHEN MATCHED AND balance < 100 THEN
-	UPDATE SET balance = balance * 2, val = t.val || ' when1'
-  WHEN MATCHED AND balance < 200 THEN
-	UPDATE SET balance = balance * 4, val = t.val || ' when2'
-  WHEN MATCHED AND balance < 300 THEN
-	UPDATE SET balance = balance * 8, val = t.val || ' when3';
+  WITH t AS (
+    MERGE INTO target_tg t
+    USING (SELECT 1 as key) s
+    ON s.key = t.key
+    WHEN MATCHED AND balance < 100 THEN
+      UPDATE SET balance = balance * 2, val = t.val || ' when1'
+    WHEN MATCHED AND balance < 200 THEN
+      UPDATE SET balance = balance * 4, val = t.val || ' when2'
+    WHEN MATCHED AND balance < 300 THEN
+      UPDATE SET balance = balance * 8, val = t.val || ' when3'
+    RETURNING t.*
+  )
+  SELECT * FROM t;
 }
 
 step "merge_delete"