```sql
CREATE OR REPLACE FUNCTION "public"."uuid_generate_v4"()  
RETURNS "pg_catalog"."uuid" AS '$libdir/uuid-ossp', 'uuid_generate_v4' 
LANGUAGE c VOLATILE STRICT  
COST 1;
```

openGauss写法
```sql
CREATE OR REPLACE FUNCTION "public"."uuid_generate_v4"() returns varchar  
LANGUAGE plpgsql  
NOT FENCED NOT SHIPPABLE  
AS $function$ DECLARE  
BEGIN  
RETURN (select upper(md5(random()::text || clock_timestamp()::text) :: varchar));  
END$function$;
```