CREATE OR REPLACE FUNCTION curr_revision()
RETURNS INTEGER
LANGUAGE plpgsql VOLATILE
AS $BODY$
DECLARE
	_revision INTEGER;
BEGIN
	BEGIN
		SELECT curr_revision INTO _revision
			FROM sys.database_info
			WHERE name = current_database();
		RETURN _revision;
	EXCEPTION WHEN OTHERS THEN
		RETURN 0;
	END;
END
$BODY$;

GRANT EXECUTE ON FUNCTION curr_revision() TO xssbook;

SELECT curr_revision();