Sphinx test with STI models

Article.rb

# == Schema Information
#
# Table name: posts
#
#  id         :integer(4)      not null, primary key
#  title      :string(255)
#  author     :text
#  content    :text
#  state      :text
#  type       :text
#  created_at :datetime
#  updated_at :datetime
#

class Article < Post

  has_many :attachments

  define_index do
    indexes attachments.filename, :as => :attachment_filenames
  end
end

Attachment.rb

# == Schema Information
#
# Table name: attachments
#
#  id         :integer(4)      not null, primary key
#  article_id :integer(4)
#  filename   :string(255)
#  created_at :datetime
#  updated_at :datetime
#

class Attachment < ActiveRecord::Base
  belongs_to :article
end

Categorization.rb

# == Schema Information
# Table name: categorizations
#
#  id          :integer(4)      not null, primary key
#  post_id     :integer(4)
#  category_id :integer(4)
#  created_at  :datetime
#  updated_at  :datetime
#

class Categorization < ActiveRecord::Base
  belongs_to :post
  belongs_to :category
end

Category.rb

# == Schema Information
# Table name: categories
#
#  id         :integer(4)      not null, primary key
#  name       :string(255)
#  created_at :datetime
#  updated_at :datetime
#

class Category < ActiveRecord::Base

  has_many :categorizations
  has_many :categories, :through => :categorizations

end

Post.rb

# == Schema Information
#
# Table name: posts
#
#  id         :integer(4)      not null, primary key
#  title      :string(255)
#  author     :text
#  content    :text
#  state      :text
#  type       :text
#  created_at :datetime
#  updated_at :datetime
#

class Post < ActiveRecord::Base

  STATES = ['pending', 'approved']

  has_many :categorizations
  has_many :categories, :through => :categorizations

  validates :state, :inclusion => { :in => STATES }

  define_index do
    indexes title
    indexes author
    indexes content
    indexes categories.name, :as => :categories_name

    has created_at, updated_at
    has categories.id, :as => :category_ids

    where "state = 'approved'"
  end
end

rails_console.out

>> ThinkingSphinx.search 'iphone', :conditions => {:title => 'post'}
ThinkingSphinx::SphinxError: query error: no field 'title' found in schema
	from /home/dia/.rvm/gems/ruby-1.9.2-p180@sandbox/gems/thinking-sphinx-2.0.5/lib/thinking_sphinx/search.rb:406:in `block in populate'
	from /home/dia/.rvm/gems/ruby-1.9.2-p180@sandbox/gems/thinking-sphinx-2.0.5/lib/thinking_sphinx/search.rb:551:in `call'
	from /home/dia/.rvm/gems/ruby-1.9.2-p180@sandbox/gems/thinking-sphinx-2.0.5/lib/thinking_sphinx/search.rb:551:in `retry_on_stale_index'
	from /home/dia/.rvm/gems/ruby-1.9.2-p180@sandbox/gems/thinking-sphinx-2.0.5/lib/thinking_sphinx/search.rb:394:in `populate'
	from /home/dia/.rvm/gems/ruby-1.9.2-p180@sandbox/gems/thinking-sphinx-2.0.5/lib/thinking_sphinx/search.rb:176:in `method_missing'
	from /home/dia/.rvm/gems/ruby-1.9.2-p180@sandbox/gems/railties-3.0.8/lib/rails/commands/console.rb:44:in `start'
	from /home/dia/.rvm/gems/ruby-1.9.2-p180@sandbox/gems/railties-3.0.8/lib/rails/commands/console.rb:8:in `start'
	from /home/dia/.rvm/gems/ruby-1.9.2-p180@sandbox/gems/railties-3.0.8/lib/rails/commands.rb:23:in `<top (required)>'
	from script/rails:6:in `require'
	from script/rails:6:in `<main>'
>> 

seeds.rb

%w[categories categorizations posts attachments].each do |table|
  ActiveRecord::Base.connection.execute("TRUNCATE #{table}")
end 

c1 = Category.create(:name => "iPhone")
c2 = Category.create(:name => "Development")
c3 = Category.create(:name => "Hiking")
c4 = Category.create(:name => "Java")

a = Article.create(:title => "Post 1", :content => "This is the content of the post", :state => 'approved')
a.categorizations.create(:category_id => c1)
a.categorizations.create(:category_id => c2)

a = Article.create(:title => "Post 2", :content => "some interesting content in the post", :state => 'pending')
a.categorizations.create(:category_id => c3)

a = Article.create(:title => "Post 3", :content => "This is the content of the post", :state => 'approved')
a.categorizations.create(:category_id => c2)
a.attachments.create(:filename => "image.png");