Function are_peers

src/backend/executor/nodeWindowAgg.c:3306–3320

* are_peers * compare two rows 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.
 */
static bool
are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
		  TupleTableSlot *slot2)
{
	WindowAgg  *node = (WindowAgg *) winstate->ss.ps.plan;
	ExprContext *econtext = winstate->tmpcontext;

	/* If no ORDER BY, all rows are peers with each other */
	if (node->ordNumCols == 0)
		return true;

	econtext->ecxt_outertuple = slot1;
	econtext->ecxt_innertuple = slot2;
	return ExecQualAndReset(winstate->ordEqfunction, econtext);
}

/*
 * window_gettupleslot