Access the database of a heroku application from another heroku application

Addon providers (of which heroku postgres is) can change the the config var they set at any time. Simply copy-and-pasting creds from one app to another will leave the second app broken when those creds are changed.

establish_connection will automatically parse a postgres URI for you, so you can just use:

    ActiveRecord::Base.establish_connection(ENV['DATABASE_URL'])

This also works for class-specific databases:

    class Photo < ActiveRecord::Base
      establish_connection(ENV['PHOTOS_DATABASE_URL'])
    end

If this is being presented as a security problem, know that this is a non-issue. This is intended behavior; Heroku config vars are considered secret. If this is just showing off that you can run multiple apps from a single database, then, yes, that too should have been clear.

I wrote this rails app that lets you look at the schemas of your other rails apps. Might be interesting to incorporate this into it.