create database testTrigger;
createlang plpgsql testtrigger;
\connect testtrigger

create table Parent( node INTEGER);
create table Child ( node INTEGER);

\d parent
\d Child

CREATE LANGUAGE plpgsql;

CREATE FUNCTION fix_child_function() RETURNS trigger AS $fix_child$
    BEGIN
        --Check ifthere were
        IF(TG_OP = 'UPDATE') THEN
            UPDATE Child SET node = NEW.node where node = OLD.node
            RETURN NEW;
        ELSIF(TG_OP = 'DELETE') THEN
            delete from Child where node = OLD.node
            RETURN NEW;
        END IF;
        RETURN NULL;
    END
$fix_child$ LANGUAGE plpgsql;

CREATE TRIGGER fix_child BEFORE UPDATE OR DELETE ON Parent FOR EACH ROW EXECUTE PROCEDURE fix_child_function();

INSERT INTO parent values(1);
INSERT INTO parent values(2);
INSERT INTO parent values(3);
INSERT INTO parent values(4);
INSERT INTO child values(2);
INSERT INTO child values(3);
INSERT INTO child values(4);

select * from parent;
select * from child;