Selecting specific columns with eager loading

I'm on Rails 2.3.5 and trying to figure out the syntax for selecting on certain columns with eager loading. For example,

class Organizer < ActiveRecord::Base
 has_many :events
end

class Event < ActiveRecord::Base
 belongs_to :organizer
 has_many :bookings
end

class Booking < ActiveRecord::Base
 belongs_to :event
end

Let's say in OrganizersController show method, I wish to use eager loading to grab certain columns from Organizer, Event, and Booking models. I believe here's the code that grabs all the columns from all 3 models

Organizer.find(params[:id], :include => {:event => {:booking}})
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But let's say that I only want to grab organizer.id, event.id, and booking.id, what's the syntax for doing so?

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Found the answer in this article.

Use :only like this, e.g.,

david.to_json(:include => { :posts => { 
                            :include => { :comments => { 
                                          :only => :body } }, 
                            :only => :title } })