ActiveRecord: :select is wiped when doing a join

I'm bumping this again with a test

class AssociationsJoinModelTest < ActiveRecord::TestCase

  def test_my_little_test
    p = Post.find(:all, :select => 'author_id, count(comments_count) as my_comment_count', :group => 'author_id', :include => :comments)
    assert p.first.respond_to?(:my_comment_count)
    
    p = Post.find(:all, :select => 'author_id, count(comments_count) as my_comment_count', :group => 'author_id', :include => :comments, :order => 'comments.type')
    assert p.first.respond_to?(:my_comment_count), :message => 'joining kills my custom select'
  
  end
end

And this is generated SQL.

First find call (Notice that eager loading is whacked too now, previous revisions worked fine though):

SELECT author_id, count(comments_count) as my_comment_count FROM `posts` GROUP BY author_id

SELECT `comments`.* FROM `comments` WHERE (`comments`.post_id IN (NULL)) ORDER BY body

Second find call:

SELECT `posts`.`id` AS t0_r0, `posts`.`author_id` AS t0_r1, `posts`.`title` AS t0_r2, `posts`.`body` AS t0_r3, `posts`.`type` AS t0_r4, `posts`.`comments_count` AS t0_r5, `posts`.`taggings_count` AS t0_r6, `comments`.`id` AS t1_r0, `comments`.`post_id` AS t1_r1, `comments`.`body` AS t1_r2, `comments`.`type` AS t1_r3 FROM `posts` LEFT OUTER JOIN `comments` ON comments.post_id = posts.id GROUP BY author_id ORDER BY comments.type

Ignore my comment about eager loading being borked, I forgot I needed to do :select => 'id' as well. Issue still stands, however.

That's the way it's always been as far as I know. Sounds like you just want :joins instead of :include.

Well, damn... You are correct. :joins actually works in this case. No reason why :include shouldn't work as well though. Rather misleading thinking that they can be used somewhat interchangeably.

No idea why I didn't try :joins right away.

Thanks :)

I fear you've rather got the wrong end of the stick. :joins just write out all those joins for you, nothing else (prior to 2.0 you'd just write out the joins yourself). :include does that and then does a lot of wiring behind the scenes so that all the associations are loaded in one go. It's that fancy wiring that requires messing with :select. It's a waste to use :include when all you needed was :joins

just noticed this - this bug actually is the cause of a bug I just added to #306 Eager fetching a HABTM fails when the HABTM uses the "include" option where eager loading relies on a column aliased as _parent_id in the :select that get clobbered because there's an :include specified

It would be helpful if ActiveRecord generated an exception if you attempted to use :select in combination with :include.