Function TupleHashTableMatch

src/backend/executor/execGrouping.c:547–571

* See whether two tuples (presumably of the same hash value) match */

 * See whether two tuples (presumably of the same hash value) match
 */
static int
TupleHashTableMatch(struct tuplehash_hash *tb, const MinimalTuple tuple1, const MinimalTuple tuple2)
{
	TupleTableSlot *slot1;
	TupleTableSlot *slot2;
	TupleHashTable hashtable = (TupleHashTable) tb->private_data;
	ExprContext *econtext = hashtable->exprcontext;

	/*
	 * We assume that simplehash.h will only ever call us with the first
	 * argument being an actual table entry, and the second argument being
	 * LookupTupleHashEntry's dummy TupleHashEntryData.  The other direction
	 * could be supported too, but is not currently required.
	 */
	Assert(tuple1 != NULL);
	slot1 = hashtable->tableslot;
	ExecStoreMinimalTuple(tuple1, slot1, false);
	Assert(tuple2 == NULL);
	slot2 = hashtable->inputslot;

	/* For crosstype comparisons, the inputslot must be first */
	econtext->ecxt_innertuple = slot2;
	econtext->ecxt_outertuple = slot1;
	return !ExecQualAndReset(hashtable->cur_eq_func, econtext);
}