Multiple database queries when chaining named scopes with rails 2.3.8 and ruby 1.9.2

Same Problem here.. It also works fine under 1.9.1p243 but not 1.9.2...

I'm using Rails 2.3.9

Group
has_many :topics, :as => :discussable (via a module)

Topic
belongs_to :discussable, :polymorphic => true named_scope :unhidden, { :conditions => ['hidden = ?', false] }

Under rails 1.9.2 without the named_scope this works properly:

reload! ; Group.find(56).topics.size

Reloading...
...snip show tables etc... Group Load (12.8ms) SELECT FROM groups WHERE (groups.id = 56) Topic Columns (13.6ms) SHOW FIELDS FROM topics SQL (81.7ms) SELECT count() AS count_all FROM topics WHERE (topics.discussable_id = 56 AND topics.discussable_type = 'Group')

However with the named scope in there:

reload! ; Group.find(56).topics.unhidden.size

Group Load (14.3ms) SELECT FROM groups WHERE (groups.id = 56) Topic Load (40.1ms) SELECT FROM topics WHERE (topics.discussable_id = 56 AND topics.discussable_type = 'Group') Topic Columns (13.5ms) SHOW FIELDS FROM topics SQL (11.8ms) SELECT count(*) AS count_all FROM topics WHERE (((hidden = 0) AND (topics.discussable_id = 56 AND topics.discussable_type = 'Group')) AND (topics.discussable_id = 56 AND topics.discussable_type = 'Group'))

So the problem is under the seond one, it selects all the topics and then
does select count(*).

Under rails 1.9.1p243 this worked correctly in both cases.

The problem appears to be when on line 146 in association proxy send gets called with "current_scoped_methods". This causes proxy_respond_to to call respond_to? which causes a method missing which causes a load_target to be called by the association collection.

/usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/base.rb:666:in find_by_sql' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/base.rb:1589:infind_every' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/base.rb:619:in find' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_collection.rb:60:infind' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_collection.rb:425:in find_target' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_collection.rb:367:inload_target' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_proxy.rb:219:in method_missing' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_collection.rb:396:inmethod_missing' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_collection.rb:343:in respond_to?' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_collection.rb:343:inproxy_respond_to?' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_proxy.rb:146:in send' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/named_scope.rb:124:ininitialize' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/named_scope.rb:90:in new' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/named_scope.rb:90:inblock in named_scope' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_collection.rb:399:in call' /usr/local/ruby19/lib/ruby/gems/1.9.1/gems/activerecord-2.3.9/lib/active_record/associations/association_collection.rb:399:inmethod_missing'

Sorry about the formatting above =)

The problem is that in association_collection, method missing is getting called with respond_to somewhere is calling respond_to_missing which is causing a new method_missing on the respond_to_missing which triggers the code path which causes the underlying collection to load.

This doesn't solve the underlying issue (dealing with the new calls to respond_to_missing?) but does act as a workaround:

--- association_collection.rb 2010-10-20 13:22:58.629947001 -0400 +++ /root/association_collection.rb 2010-10-20 13:22:54.509947004 -0400 @@ -390,7 +390,7 @@

         if block_given?
           super { |*block_args| yield(*block_args) }
         else

•        super
  

•        super unless method.to_s == "respond_to_missing?"
       end
     elsif @reflection.klass.scopes.include?(method)
       @reflection.klass.scopes[method].call(self, *args)
  

Stephen, thanks for the workaround. I created the attached rails initializer file and the problem seems to be fixed. I am still concerned however about the new calls to repsond_to_missing as you mentioned, and if this workaround causes issues elsewhere...

Got it, thanks for the info. Any idea when/if this patch will be applied to 2.3?

Can anyone run the tests for ActiveRecord under 1.9.2? I can not, and created ticket 5887. I verified that this patch does somewhat speed up my app's testing under 1.9.2, but it's still slow and I would like to profile by running the tests and possibly find a few more places that need 1.9.2 help.

Link to ticket #5887 Can not run ActiveRecord tests under 1.9.2
#5887 Can not run ActiveRecord tests under 1.9.2