Fix cross-type case in partial row matching for hashed subplans.

When hashing a subplan like "WHERE (a, b) NOT IN (SELECT x, y FROM ...)",
findPartialMatch() attempted to match rows using the hashtable's internal
equality operators, which of course are for x and y's datatypes.  What we
need to use are the potentially cross-type operators for a=x, b=y, etc.
Failure to do that leads to wrong answers or even crashes.  The scope for
problems is limited to cases where we have different types with compatible
hash functions (else we'd not be using a hashed subplan), but for example
int4 vs int8 can cause the problem.

Per bug #7597 from Bo Jensen.  This has been wrong since the hashed-subplan
code was written, so patch all the way back.

src/backend/executor/nodeSubplan.c

@@ -37,7 +37,8 @@ static Datum ExecScanSubPlan(SubPlanState *node,
 				ExprContext *econtext,
 				bool *isNull);
 static void buildSubPlanHash(SubPlanState *node, ExprContext *econtext);
-static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot);
+static bool findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
+				 FmgrInfo *eqfunctions);
 static bool slotAllNulls(TupleTableSlot *slot);
 static bool slotNoNulls(TupleTableSlot *slot);
 
@@ -140,7 +141,7 @@ ExecHashSubPlan(SubPlanState *node,
 			return BoolGetDatum(true);
 		}
 		if (node->havenullrows &&
-			findPartialMatch(node->hashnulls, slot))
+			findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
 		{
 			ExecClearTuple(slot);
 			*isNull = true;
@@ -173,14 +174,14 @@ ExecHashSubPlan(SubPlanState *node,
 	}
 	/* Scan partly-null table first, since more likely to get a match */
 	if (node->havenullrows &&
-		findPartialMatch(node->hashnulls, slot))
+		findPartialMatch(node->hashnulls, slot, node->cur_eq_funcs))
 	{
 		ExecClearTuple(slot);
 		*isNull = true;
 		return BoolGetDatum(false);
 	}
 	if (node->havehashrows &&
-		findPartialMatch(node->hashtable, slot))
+		findPartialMatch(node->hashtable, slot, node->cur_eq_funcs))
 	{
 		ExecClearTuple(slot);
 		*isNull = true;
@@ -560,9 +561,13 @@ buildSubPlanHash(SubPlanState *node, ExprContext *econtext)
  * We have to scan the whole hashtable; we can't usefully use hashkeys
  * to guide probing, since we might get partial matches on tuples with
  * hashkeys quite unrelated to what we'd get from the given tuple.
+ *
+ * Caller must provide the equality functions to use, since in cross-type
+ * cases these are different from the hashtable's internal functions.
  */
 static bool
-findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot)
+findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot,
+				 FmgrInfo *eqfunctions)
 {
 	int			numCols = hashtable->numCols;
 	AttrNumber *keyColIdx = hashtable->keyColIdx;
@@ -575,7 +580,7 @@ findPartialMatch(TupleHashTable hashtable, TupleTableSlot *slot)
 		ExecStoreMinimalTuple(entry->firstTuple, hashtable->tableslot, false);
 		if (!execTuplesUnequal(slot, hashtable->tableslot,
 							   numCols, keyColIdx,
-							   hashtable->cur_eq_funcs,
+							   eqfunctions,
 							   hashtable->tempcxt))
 		{
 			TermTupleHashIterator(&hashiter);

src/test/regress/expected/subselect.out

@@ -506,6 +506,23 @@ from
 -----
 (0 rows)
 
+--
+-- Test case for cross-type partial matching in hashed subplan (bug #7597)
+--
+create temp table outer_7597 (f1 int4, f2 int4);
+insert into outer_7597 values (0, 0);
+insert into outer_7597 values (1, 0);
+insert into outer_7597 values (0, null);
+insert into outer_7597 values (1, null);
+create temp table inner_7597(c1 int8, c2 int8);
+insert into inner_7597 values(0, null);
+select * from outer_7597 where (f1, f2) not in (select * from inner_7597);
+ f1 | f2 
+----+----
+  1 |  0
+  1 |   
+(2 rows)
+
 --
 -- Test case for premature memory release during hashing of subplan output
 --

src/test/regress/sql/subselect.sql

@@ -329,6 +329,21 @@ from
   join
   int4_tbl i4 on dummy = i4.f1;
 
+--
+-- Test case for cross-type partial matching in hashed subplan (bug #7597)
+--
+
+create temp table outer_7597 (f1 int4, f2 int4);
+insert into outer_7597 values (0, 0);
+insert into outer_7597 values (1, 0);
+insert into outer_7597 values (0, null);
+insert into outer_7597 values (1, null);
+
+create temp table inner_7597(c1 int8, c2 int8);
+insert into inner_7597 values(0, null);
+
+select * from outer_7597 where (f1, f2) not in (select * from inner_7597);
+
 --
 -- Test case for premature memory release during hashing of subplan output
 --