Rails Issue #8811

Gemfile

source "https://rubygems.org"

gem "sqlite3"
gem "rails", :git => 'https://github.com/rails/rails.git', :branch => '3-2-stable'

test.rb

require 'bundler'

Bundler.require

require 'active_record'

ActiveRecord::Base.establish_connection adapter: "sqlite3", database: ":memory:"
ActiveRecord::Base.logger = Logger.new(STDOUT)

ActiveRecord::Migration.suppress_messages do
  ActiveRecord::Schema.define(:version => 0) do

    create_table "categories", :force => true do |t|
      t.string   "name"
      t.datetime "created_at", :null => false
      t.datetime "updated_at", :null => false
    end

    create_table "product_category_relations", :force => true do |t|
      t.integer  "product_id"
      t.integer  "category_id"
      t.datetime "created_at",  :null => false
      t.datetime "updated_at",  :null => false
    end

    create_table "products", :force => true do |t|
      t.string   "name"
      t.datetime "created_at", :null => false
      t.datetime "updated_at", :null => false
    end
  end
end


class Category < ActiveRecord::Base
  has_many :product_category_relations, :dependent => :destroy
end

class Product < ActiveRecord::Base
  has_many :categories, :through => :product_category_relations
  has_many :product_category_relations, :dependent => :destroy
end

class ProductCategoryRelation < ActiveRecord::Base
  belongs_to :product
  belongs_to :category
end

cat1 = Category.create!(:name => 'category1')
cat2 = Category.create!(:name => 'category2')

p = Product.new(:name => 'product1')
p.categories << [cat1, cat2]
p.save!