epgsql: invalid_password

I’m writing a simple web application in Erlang that uses epgsql to talk to a PostgreSQL database. I keep getting invalid_password, despite the fact that the user doesn’t have a password (and I’m passing “”). I can also log in by using psql -U foo.

Huh?

Turns out that the epgsql driver connects over TCP, rather than the unix domain socket used by psql. You also need to add the following to pg_hba.conf:

host    all     foo     127.0.0.1/32    trust

Sorted.