Eager loading of polymorphic associations doesn't work in Rails < 2.1 and only works in 2.1 if rails doesn't have to fall back on left outer joins for the :include.

This plugin allows eager loading in all situations in rails.

It assumes you are using the default "_type" suffix. With this code you can just use a :include directive in your finds and it will return your associations instead of throwing an exception.

To install as a rails plugin, use the script/plugin command with rails >= 2.0

./script/plugin install git://github.com/haruska/polymorphic_include.git

For rails < 2.0, install it by hand

cd vendor/plugins
git clone git://github.com/haruska/polymorphic_include.git

class Address < ActiveRecord::Base
  belongs_to :addressable, :polymorphic => true
end

# A call that tries to eager load the addressable model
Address.find(:all, :include => :addressable)

Copyright (c) 2008-2009 Jason Haruska, released under the MIT license