Function append_total_cost_compare

src/backend/optimizer/util/pathnode.c:1538–1549

* append_total_cost_compare * list_sort comparator for sorting append child paths * by total_cost descending * * For equal total costs, we fall back to comparing startup costs; if those * are equal too, break ties using bms_compare on the paths' relids. * (This is to avoid getting unpredictable results from list_sort.) */

 * (This is to avoid getting unpredictable results from list_sort.)
 */
static int
append_total_cost_compare(const ListCell *a, const ListCell *b)
{
	Path	   *path1 = (Path *) lfirst(a);
	Path	   *path2 = (Path *) lfirst(b);
	int			cmp;

	cmp = compare_path_costs(path1, path2, TOTAL_COST);
	if (cmp != 0)
		return -cmp;
	return bms_compare(path1->parent->relids, path2->parent->relids);
}

/*
 * append_startup_cost_compare