Using preload associations

gistfile1.rb

class Comment < ActiveRecord::Base
  def self.preload_graffities_associations(graffities)
    # We want to load the following data
    # associations = [{:user => :profile}, {:replys => {:user => :profile}}]
    # We join graffities and replys to load its users and profile to avoid two querys
    graffities_and_replys = (graffities + graffities.map(&:replys)).flatten
    Comment.send(:preload_associations, graffities_and_replys, {:user => :profile})
  end
end
 
graffities = profile.graffities
  Comment Load (15.9ms) SELECT * FROM `comments` WHERE (`comments`.commentable_id = 3 AND `comments`.commentable_type = 'Profile' AND (parent_id IS NULL)) LIMIT 1
  Comment Load (14.5ms) SELECT * FROM `comments` WHERE (`comments`.parent_id = 2) ORDER BY created_at DESC
+----+----------------+------------------+-------+---------------------+---------+---------+-----------+-----+-----+-------------------------+-------------------------+
| id | commentable_id | commentable_type | title | body                | subject | user_id | parent_id | lft | rgt | created_at              | updated_at              |
+----+----------------+------------------+-------+---------------------+---------+---------+-----------+-----+-----+-------------------------+-------------------------+
| 4  | 3              | Profile          |       | Esto es un graffity |         | 1       | 2         | 2   | 7   | 2009-12-12 17:35:54 UTC | 2009-12-12 17:35:54 UTC |
+----+----------------+------------------+-------+---------------------+---------+---------+-----------+-----+-----+-------------------------+-------------------------+
 
 
Comment.preload_graffities_associations(graffities)
  Comment Load (0.5ms) SELECT * FROM `comments` WHERE (`comments`.parent_id = 4) ORDER BY created_at ASC
  User Load (0.1ms) SELECT * FROM `users` WHERE (`users`.`id` IN (1,3))
  Profile Load (0.1ms) SELECT `profiles`.* FROM `profiles` WHERE (`profiles`.user_id IN (1,3))