ruby-on-rails - Rails ActiveRecord::find Join语句问题

Question

为什么下面的Rails声明

User.find(:all, :joins => [:roles,:roles_users], 
          :conditions => { :roles => { :name => 'subscriber', 
                                       :authorizable_id => self.id, 
                                       :authorizable_type => self.class.to_s }})

转换为此(使用2x相同的连接)

SELECT "users".* FROM "users" 
    JOIN "roles_users" ON ("users"."id" = "roles_users"."user_id") 
    JOIN "roles" ON ("roles"."id" = "roles_users"."role_id") 
    JOIN "roles_users" roles_users_users ON roles_users_users.user_id = users.id 
  WHERE ("roles"."authorizable_id" = 4 AND "roles"."name" = 'subscriber' AND "roles"."authorizable_type" = 'Howto') 

只是好奇。

Answer 1

我不需要加入Roles_users，因为该插件已经做了一次...

谢谢你的帮助。

has_many :users, :finder_sql => 'SELECT DISTINCT users.* FROM users INNER JOIN roles_users ON user_id = users.id INNER JOIN roles ON roles.id = role_id WHERE authorizable_type = \'#{self.class.base_class.to_s}\' AND authorizable_id = #{id}', :counter_sql => 'SELECT COUNT(DISTINCT users.id) FROM users INNER JOIN roles_users ON user_id = users.id INNER JOIN roles ON roles.id = role_id WHERE authorizable_type = \'#{self.class.base_class.to_s}\' AND authorizable_id = #{id}', :readonly => true