I usually prefer pg_cancel_backend because it seems.. nicer, but lately I've had a troublesome user who leaves transactions open and I've scripted up a call to pg_terminate_backend after 60 minutes in an idle transaction. It works well.
Question: is there any server impact beyond that user's transaction when calling pg_terminate_backend? I feel like there _used_ to be, maybe in PG9, where I recall maybe seeing a server disconnect or something when using terminate.