ALTER TABLE node ADD COLUMN updated TIMESTAMP NOT NULL DEFAULT NOW();

CREATE OR REPLACE FUNCTION node_update_timestamp()
RETURNS TRIGGER
LANGUAGE PLPGSQL
AS $$
BEGIN
	IF NEW.updated = OLD.updated THEN
		UPDATE node SET updated = NOW() WHERE id=NEW.id;
	END IF;
	RETURN NEW;
END;
$$;

CREATE OR REPLACE TRIGGER node_update AFTER UPDATE ON node
FOR EACH ROW
EXECUTE PROCEDURE node_update_timestamp()