PostgreSQL Server Programming - Second Edition

Preventing schema changes

Another common use case for event triggers is to prevent the execution of certain commands based on a specific condition. If you only want to stop users from executing some commands, you can always revoke the privileges using more conventional means. The triggers may come in handy if you want to do this based on a certain condition, let's say, time of the day:

CREATE OR REPLACE FUNCTION abort_create_table_func() RETURNS event_trigger AS $$ DECLARE current_hour int := extract(hour from now()); BEGIN if current_hour BETWEEN 9 AND 16 then RAISE EXCEPTION 'Not a suitable time to create tables'; end if; END; $$ LANGUAGE plpgsql SECURITY DEFINER; CREATE EVENT TRIGGER abort_create_table ON ddl_command_start WHEN TAG IN ('CREATE ...