从树状结构中获取所有子节点(邻接列表模型)

CREATE OR REPLACE FUNCTION get_categories_all_children(use_parent INT4) RETURNS INT4[] AS $$
DECLARE
    process_parents INT4[] := ARRAY[ use_parent ];
    children INT4[] := '{}';
    new_children INT4[];
BEGIN
    WHILE ( array_upper( process_parents, 1 ) IS NOT NULL ) LOOP
        new_children := ARRAY( SELECT id FROM categories WHERE parent_id = ANY( process_parents ) AND id <> ALL( children ) );
        children := children || new_children;
        process_parents := new_children;
    END LOOP;
    RETURN children;
END;
$$ LANGUAGE plpgsql;