DROP TRIGGER waterway_axis_wtwaxs_unique ON waterway.waterway_axis;

CREATE CONSTRAINT TRIGGER waterway_axis_wtwaxs_unique
    AFTER INSERT OR UPDATE OF wtwaxs, validity ON waterway.waterway_axis
    DEFERRABLE INITIALLY DEFERRED
    FOR EACH ROW
    EXECUTE FUNCTION prevent_st_equals('wtwaxs', 'validity WITH &&');