Combine MongoDB and Postgresql in Rails?

Question

Is it possible to combine AR with MongoMapper/MongoID?

If so, are there tutorials/documentations for this?

Answer 1

Yes, it is a piece of cake. There really isn't anything special you need to do, just make models with the different adapters accordingly. This is an example Mongoid document:

class Project
  include Mongoid::Document
end

For comparison, here is activerecord:

class BillingEntry < ActiveRecord::Base
end

Just make sure not to mix them up. For example, don't include mongoid on a class that inherits from ActiveRecord::Base. I recommend Rails 3, as it's probably going to release this week, and the RCs have been really solid so far.