Postgres table changes listen notify

foo.sql

DROP TABLE IF EXISTS foo ;
CREATE TABLE foo(
    id serial primary key,
    body text
);

INSERT INTO foo (body) values ('blabal');


CREATE OR REPLACE FUNCTION notify_trigger() RETURNS trigger AS $$
DECLARE
  rec record;
  dat record;
  channel TEXT;
  delete_channel TEXT;
  payload TEXT;
BEGIN
  channel := TG_TABLE_NAME || '_';
  CASE TG_OP
  WHEN 'UPDATE' THEN
     rec := NEW;
     channel := channel || 'update_' || rec.id;
  WHEN 'INSERT' THEN
     rec := NEW;
     channel := channel || 'insert';
  WHEN 'DELETE' THEN
     rec := OLD;
     delete_channel := channel || 'delete_' || rec.id;
     channel := channel || 'delete';
  ELSE
     RAISE EXCEPTION 'Unknown TG_OP: "%". Should not occur!', TG_OP;
  END CASE;
  payload := json_build_object(
    'timestamp',
    CURRENT_TIMESTAMP,
    'record',
    row_to_json(rec)
  );
  PERFORM pg_notify(channel, payload);
  if delete_channel IS NOT NULL then
    PERFORM pg_notify(delete_channel, payload);
  end if;
  RETURN rec;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE TRIGGER foo_notify AFTER INSERT OR UPDATE OR DELETE ON foo
FOR EACH ROW EXECUTE PROCEDURE notify_trigger();

CREATE OR REPLACE FUNCTION foo_listen() RETURNS VOID AS $$
DECLARE
  row_id varchar;
BEGIN
    FOR row_id in SELECT id::varchar FROM foo LOOP
        execute format('LISTEN %I', 'foo_' || row_id);
        execute format('LISTEN %I', 'foo_delete_' || row_id);
    END LOOP;
    LISTEN foo_insert;
    LISTEN foo_delete;
END
$$ LANGUAGE plpgsql;

SELECT foo_listen() as output;