Function WinRowsArePeers

src/backend/executor/nodeWindowAgg.c:3529–3566

* WinRowsArePeers * Compare two rows (specified by absolute position in partition) to see * if they are equal according to the ORDER BY clause. * * NB: this does not consider the window frame mode. */

 * NB: this does not consider the window frame mode.
 */
bool
WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2)
{
	WindowAggState *winstate;
	WindowAgg  *node;
	TupleTableSlot *slot1;
	TupleTableSlot *slot2;
	bool		res;

	Assert(WindowObjectIsValid(winobj));
	winstate = winobj->winstate;
	node = (WindowAgg *) winstate->ss.ps.plan;

	/* If no ORDER BY, all rows are peers; don't bother to fetch them */
	if (node->ordNumCols == 0)
		return true;

	/*
	 * Note: OK to use temp_slot_2 here because we aren't calling any
	 * frame-related functions (those tend to clobber temp_slot_2).
	 */
	slot1 = winstate->temp_slot_1;
	slot2 = winstate->temp_slot_2;

	if (!window_gettupleslot(winobj, pos1, slot1))
		elog(ERROR, "specified position is out of window: " INT64_FORMAT,
			 pos1);
	if (!window_gettupleslot(winobj, pos2, slot2))
		elog(ERROR, "specified position is out of window: " INT64_FORMAT,
			 pos2);

	res = are_peers(winstate, slot1, slot2);

	ExecClearTuple(slot1);
	ExecClearTuple(slot2);

	return res;
}

/*
 * WinGetFuncArgInPartition