title: How to check if trigger exists in PostgreSQL?
body: <p>I want to verify correctness of database migrations which add triggers to some tables. I'm using <a href="http://sqitch.org" rel="noreferrer">sqitch</a>, so I'd like to find a way to check it with SQL queries. I believe it should be possible with postgres system tables, but I currently can't find a way to do this.</p>