CREATE or REPLACE FUNCTION "sys_guid"()
RETURNS "pg_catalog"."varchar" AS
$BODY$
DECLARE
v_seed_value varchar(32);
BEGIN
select
md5(
inet_client_addr()::varchar ||
timeofday() ||
inet_server_addr()::varchar ||
to_hex(inet_client_port())
)
into v_seed_value;


return (substr(v_seed_value,1,8) ||
substr(v_seed_value,9,4) ||
substr(v_seed_value,13,4) ||
substr(v_seed_value,17,4) ||
substr(v_seed_value,21,12));
END;
$BODY$
LANGUAGE ‘plpgsql‘ VOLATILE SECURITY DEFINER;

postgresql支持sys_guid()