title: Check if a user-defined type already exists in PostgreSQL
body: <p>Say I have created some user-defined types in the DB, </p>
  
  <p>i.e. <code>CREATE TYPE abc ...</code></p>
  
  <p>Is it then possible to determine if the user-defined type exists or not? Perhaps, using any of the postgres information tables?</p>
  
  <p>The main reason for this is since PostgreSQL does not seem to support <code>CREATE OR REPLACE TYPE ...</code>, and if a certain type gets created more than once, I want to be able to drop the existing one first, then re-load the new one.</p>