Function to send a Postgres Notification with a JSON object payload of the updated fields. Also the trigger to call the function.

trigger_and_function.sql

CREATE OR REPLACE FUNCTION send_notification() RETURNS trigger AS $$
BEGIN
  PERFORM pg_notify('usersupdate', 
    (SELECT row_to_json(r.*)::varchar FROM (
      SELECT id, email, name from users where id = NEW.id)
    r)
  );
  RETURN NEW;
END;
$$ LANGUAGE plpgsql;


CREATE TRIGGER users_updated
  AFTER UPDATE OF email,name
  ON users
  FOR EACH ROW
  EXECUTE PROCEDURE send_notification();