Rails core - Dec 2006 - weird count behaviour in has_many :through relationship

The counter is not working as I expected in has_many :through
relationship. I''ve posted this to Ruby on Rails: Talk, too, but
nobody seems to know about this.

I have very simple models. The Article and Pubtype models are in
many-to-many relationship, which is stored in the ArticleType model.

Here are the models:

class Article < ActiveRecord::Base
  has_many :article_types
  has_many :pubtypes, :through => :article_types
end

class Pubtype < ActiveRecord::Base
  has_many :article_types
  has_many :articles, :through => :article_types
end

class ArticleType < ActiveRecord::Base
  belongs_to :article
  belongs_to :pubtype
end

Here is the actual schema:

ActiveRecord::Schema.define(:version => 8) do
...
  create_table "article_types", :force => true do |t|
    t.column "article_id", :integer
    t.column "pubtype_id", :integer
  end

  create_table "articles", :force => true do |t|
    t.column "title",            :text
  end

  create_table "pubtypes", :force => true do |t|
    t.column "title",          :string
    t.column "articles_count", :integer, :default => 0, :null =>
false
  end
...
end

And here is the weird situation (''>>'' is irb and
''##'' is log):
>> pubtype = Pubtype.find(1)
=> #<Pubtype:0x337a728
@attributes={"title"=>"News",
"id"=>"1",
"articles_count"=>"1"}>

## Pubtype Load (0.000559)   SELECT * FROM pubtypes WHERE (pubtypes.id
= 1)
>> pubtype.articles_count
=> 1

## Article Load (0.008023)   SELECT articles.* FROM articles INNER JOIN
article_types ON articles.id = article_types.article_id WHERE
((article_types.pubtype_id = 1))

Here, the already loaded "articles_count" attribute value of the
pubtype object is not used and a actual select sql was called to count
the number of articles that belong to the pubtype. It seems that rails
intercepted the method call and did an unnecessary magic.

Is this an intentional behaviour for some good reason?

I''m running on the edge rails.

About your application''s environment
Ruby version                 1.8.5 (i686-darwin8.8.1)
RubyGems version             0.9.0
Rails version                1.2.0
Active Record version        1.14.4
Action Pack version          1.12.5
Action Web Service version   1.1.6
Action Mailer version        1.2.5
Active Support version       1.3.1
Edge Rails revision          5717
Application root             /Users/joon/Sites/clickstream
Environment                  development
Database adapter             mysql
Database schema version      8


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