PostgreSQL is running locally but I cannot connect. Why?

I found that I had an extremely similar problem, namely that postgres was opening a socket in /var/pgsql_socket_alt where none of my software expects to look, but the solution to my problem was not only a problem with my $PATH.

I had to create the directory /var/pgsql_socket, chown it to myself, and set unix_socket_directory in postgresql.conf (located in /usr/local/var/postgres) to that directory, then use the pg_ctl binary in /usr/local/bin to start the right postgres server successfully (which is where $PATH comes in – make sure which pg_ctl resolves to /usr/local/bin/pg_ctl, or just always call it explicitly).

This might help other users who find this question via the /var/pgsql_socket_alt mention.

A plausible and typical explanation would be that the psql that comes with homebrew is in /usr/local/bin/psql which is different from the one that would be in your $PATH, like /usr/bin/psql (bundled with OS X). You may want to try with the full path:

$ /usr/local/bin/psql -U rails -d myapp_development

Also, there's something rather unusual in the ps output of your question: the postgres server is running under a meltemi Unix user, whereas generally, the dedicated postgres Unix user is used for that.

I don't know of any config file for the psql client. However psql does respect a number of environment variables that correlate to command line options.

So to have the psql automatically use the socket of your choice you can set the PGHOST variable to the directory containing the socket. i.e.

PGHOST=/var/pgsql_socket_alt
psql -d mydatabsase