Lately, my prefered Postgres distribution of choice for OSX is Postgres.app.

Its very easy to download and install (just drag-n-drrop, like most other OSX Apps), no need to wait for it to compile, and it comes with a nice menubar icon for control.

In its default configuration it only listens on a port, but not on a unix socket. The problem is, Rails recipes with postgres create a config/database.yml file that assumes a socket presence.

Of example:

✗ rails new test1 -d postgresql
      create
      create  README.rdoc
      ...
Your bundle is complete!
Use `bundle show [gemname]` to see where a bundled gem is installed.
✗ cd test1
✗ rake db:create
could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/pgsql_socket/.s.PGSQL.5432"?

This problem was bothering me for a while as I tried to use rails_apps_composer to bootstrap new applications and it was failing on those database errors.

I didn’t want to mess with Postgres.app configs, as I suspected they’d be overwriten on each version upgrade, so at first I tried to somehow trick it to stop and let me replace the config/database.yml file in time. The solution turned out to be much simpler though.

The Rails Postgres driver recognizes standard Postgres environment variables, one of which is PGHOST. When set to localhost Rails will go for the port instead of the Unix socket, even if there is no host: localhost setting in the YAML file.

✗ PGHOST=localhost rake db:create
✗ _

So just add export PGHOST=localhost to your shell start file, e.g. ~/.zshrc and you are set.

Im actually went further with it, and now I have shell aliases to reset postgres env config, configure it for localhost, or read current application Heroku configs and pre-set Postgres environment for a direct access to Heroku db, but that is a topic for another blog post.