UPDATE pg_language SET lanpltrusted = true WHERE lanname LIKE 'plr';
You seem to be missing the point. The language is either trusted, or it's not. Modifying the catalogs is not part of a "good flow", ever. In short, "don't use trusted languages ever". If a specific requirement can only be implemented using a trusted language maybe there is a reason to use it - in development and production (if your DBA will let you) - but more likely you are better off writing an out-of-database client application and doing the "trusted" stuff there.