CREATE OR REPLACE FUNCTION parent_paths (path ltree) RETURNS SETOF ltree AS $$
DECLARE
	i INTEGER;
	level INTEGER;
	subpath ltree;
BEGIN

	SELECT nlevel (path) INTO level;

	FOR i IN 1 .. level LOOP
		SELECT subpath(path, 0, i) INTO subpath;
		RETURN NEXT subpath;
	END LOOP;
	
	RETURN level;
END;
$$ LANGUAGE plpgsql WITH (ISCACHABLE);