gistfile1.rb

module AfterTransaction
  def self.included(base)
    base.extend(ClassMethods)

    base.class_eval do
      class <<self
        alias_method_chain :transaction, :callbacks
      end
    end
  end

  module ClassMethods
    @@after_transaction_hooks = []

    def transaction_with_callbacks(&block)
      clean = true
      transaction_without_callbacks(&block)
    rescue Exception
      clean = false
      raise
    ensure
      if connection.open_transactions.zero?
        after_transaction_callbacks if clean
        clear_transaction_callbacks!
      end
    end

    def after_transaction(&block)
      if connection.open_transactions.zero?
        yield
      else
        @@after_transaction_hooks << block
      end
    end

    private

      def after_transaction_callbacks
        @@after_transaction_hooks.each { |hook| hook.call }
      end

      def clear_transaction_callbacks!
        @@after_transaction_hooks.clear
      end
  end
  
  def after_transaction(&block)
    self.class.after_transaction(&block)
  end
end

ActiveRecord::Base.send(:include, AfterTransaction)