"Pedro Fonseca" <pedro(dot)fonseca(at)netcabo(dot)pt> writes:
> In short: I'd like this database accessible only by *one* PostgreSQL user
> (instead of all), I don't want this user to have to authenticate through a
> password and I don't want to use TCP/IP.
Possibly setting restrictive permissions on the socket file is the way
to go (see the unix_socket parameters in postgresql.conf). pg_hba will
certainly not help you here, but if you can set up an /etc/group entry
with only the authorized users as its members, you're set.
regards, tom lane