title: Postgresql session's custom parameter
body: <p>To log table data changes in the PostgreSQL DB I created triggers on table ON UPDATE and ON INSERT, however besides having what is changed I want to know who changed it, but the site code is using one "DB user" to connect to DB, which I can get via CURRENT_USER variable. How can I attach some parameter("site user" name) to a DB session, so later I can get it in DB in triggers function. On the site site I'm using SQLAlchemy.</p>