Function MemoizeHash_equal

src/backend/executor/nodeMemoize.c:215–259

* MemoizeHash_equal * Equality function for confirming hash value matches during a hash * table lookup. 'key2' is never used. Instead the MemoizeState's * probeslot is always populated with details of what's being looked up. */

 *		probeslot is always populated with details of what's being looked up.
 */
static bool
MemoizeHash_equal(struct memoize_hash *tb, const MemoizeKey *key1,
			  const MemoizeKey *key2)
{
	MemoizeState *mstate = (MemoizeState *) tb->private_data;
	ExprContext *econtext = mstate->ss.ps.ps_ExprContext;
	TupleTableSlot *tslot = mstate->tableslot;
	TupleTableSlot *pslot = mstate->probeslot;

	/* probeslot should have already been prepared by prepare_probe_slot() */
	ExecStoreMinimalTuple(key1->params, tslot, false);

	if (mstate->binary_mode)
	{
		int			numkeys = mstate->nkeys;

		slot_getallattrs(tslot);
		slot_getallattrs(pslot);

		for (int i = 0; i < numkeys; i++)
		{
			FormData_pg_attribute *attr;

			if (tslot->tts_isnull[i] != pslot->tts_isnull[i])
				return false;

			/* both NULL? they're equal */
			if (tslot->tts_isnull[i])
				continue;

			/* perform binary comparison on the two datums */
			attr = &tslot->tts_tupleDescriptor->attrs[i];
			if (!datum_image_eq(tslot->tts_values[i], pslot->tts_values[i],
								attr->attbyval, attr->attlen))
				return false;
		}
		return true;
	}
	else
	{
		econtext->ecxt_innertuple = tslot;
		econtext->ecxt_outertuple = pslot;
		return ExecQualAndReset(mstate->cache_eq_expr, econtext);
	}
}

/*
 * Initialize the hash table to empty.