test case demonstrating uniq-through associations don't remove order anymore (which breaks postgresql)

uniq_through.rb

# gem 'activerecord', '3.2.16'  # works
gem 'activerecord', '4.0.2' # breaks
require 'active_record'
require 'minitest/autorun'
require 'logger'

Minitest::Test = MiniTest::Unit::TestCase unless defined?(Minitest::Test)

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

ActiveRecord::Schema.define do
  create_table :posts do |t|
  end

  create_table :comments do |t|
    t.integer :post_id
    t.integer :user_id
  end

  create_table :users do |t|
  end
end

class Post < ActiveRecord::Base
  if Gem.loaded_specs["activerecord"].version.to_s >= "4"
    has_many :comments, -> {order(:id)}
    has_many :uniq_users_with_reorder, -> {reorder("").uniq},    :through => :comments, :source => :user
    has_many :uniq_users_with_except,  -> {except(:order).uniq}, :through => :comments, :source => :user
    has_many :uniq_users,              -> {uniq},                :through => :comments, :source => :user
  else
    has_many :comments, :order => :id
    has_many :uniq_users,                 :uniq => true,         :through => :comments, :source => :user
  end
end

class Comment < ActiveRecord::Base
  belongs_to :post
  belongs_to :user
end

class User < ActiveRecord::Base
end

class BugTest < Minitest::Test
  def test_uniq_through_removes_order_to_work_with_postgresql
    post = Post.create!

    if Gem.loaded_specs["activerecord"].version.to_s >= "4"
      
      # reorder("") should work, i.e. overwrite order from relation
      assert(!(post.uniq_users_with_reorder.to_sql =~ /order by/i), "generated sql includes ORDER BY")

      # except(:order) should work, i.e. remove order from relation
      assert(!(post.uniq_users_with_except.to_sql  =~ /order by/i), "generated sql includes ORDER BY")

      # possibly nice to have: uniq() automatically removes order from relation
      assert(!(post.uniq_users.to_sql              =~ /order by/i), "generated sql includes ORDER BY")

    else

      # just works: uniq() automatically removes order from relation
      assert(!(post.uniq_users.to_sql              =~ /order by/i), "generated sql includes ORDER BY")
      
    end
  end
end