Good find! I've seen similar behavior before and was wondering why it wasn't easy to stop.

This isn't the only place Postgres can act like this, though. I've seen similar behavior when a foreign data wrapper times out or loses connection, and had to resort to either using kill -9 or attaching to the process using a debugger and closing the socket, which oddly enough also worked.

Might be worth generalizing this approach to also handle that kind of failure