Function reorderqueue_cmp

src/backend/executor/nodeIndexscan.c:444–456

* Pairing heap provides getting topmost (greatest) element while KNN provides * ascending sort. That's why we invert the sort order. */

 * ascending sort.  That's why we invert the sort order.
 */
static int
reorderqueue_cmp(const pairingheap_node *a, const pairingheap_node *b,
				 void *arg)
{
	ReorderTuple *rta = (ReorderTuple *) a;
	ReorderTuple *rtb = (ReorderTuple *) b;
	IndexScanState *node = (IndexScanState *) arg;

	/* exchange argument order to invert the sort order */
	return cmp_orderbyvals(rtb->orderbyvals, rtb->orderbynulls,
						   rta->orderbyvals, rta->orderbynulls,
						   node);
}

/*
 * Helper function to push a tuple to the reorder queue.