default_scope breaks (update|delete|destroy)_all in some cases

Rails 3.

The code posted below, is purely for illustration of this problem. Hopefully this does not confuse the issue.

Given I have a Post model, and a Comment model. Post has_many Comments, and Comment belongs_to Post.

With a default_scope set on the Post model, defining joins() and where() relations. In this case where() is dependent on joins().

Normally Posts wouldn't be dependent on Comments. Again, I just want to give a simple example. This could be any case when where() is dependent on joins() or other methods.

    class Post < ActiveRecord::Base
      has_many :comments, :dependent => :destroy
      
      default_scope joins(:comments).where("comments.id < 999")
    end

    class Comment < ActiveRecord::Base
      belongs_to :post, :counter_cache => true
    end

Running the following command:

    Post.update_all(:title => Time.now)

Produces the following query, and ultimately throws ActiveRecord::StatementInvalid:

    UPDATE `posts` SET `title` = '2010-10-15 15:59:27'  WHERE (comments.id < 999)

Again, update_all, delete_all, destroy_all behave the same way. I discovered this behaviour when my application complained when trying to update the counter_cache. Which eventually drills down into update_all.