Preventing N+1 queries in Rails

Question

I\'ve seen a few examples of passing an :include hash value when calling one of ActiveRecord\'s find methods in Rails. However, I haven\'t seen any

Answer 1

You can't use relations as Class methods. It is instance methods. You can call

@user.favorites

Check out this screencast about Eager Loading

http://railscasts.com/episodes/22-eager-loading

It will be

 User.find(:all, :include => :favorites)

or for Rails 3.x

 User.includes(:favorites)

Answer 2

You can add :include to your model's associations to eager load the second-order associations when the object is loaded.

http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-belongs_to http://api.rubyonrails.org/classes/ActiveRecord/Associations/ClassMethods.html#method-i-has_many