lock tables from being altered in postgres

disable_ddl_ops.sql

CREATE OR REPLACE FUNCTION schema.ddl_issue()
 RETURNS event_trigger
 LANGUAGE plpgsql
AS $function$
DECLARE r RECORD;
BEGIN
    FOR r IN SELECT * FROM pg_event_trigger_ddl_commands() LOOP
      IF ( r.objid::regclass::text = 'schema.tablename' )
      THEN
            RAISE EXCEPTION 'You are not allowed to change %', r.object_identity;
      END IF;
    END LOOP;
END;
$function$
;

-- event trigger

CREATE EVENT TRIGGER no_ddl_allowed
  ON ddl_command_end WHEN TAG IN ('ALTER TABLE')
  EXECUTE PROCEDURE  schema.ddl_issue();