rollback_transaction

# File activerecord/lib/active_record/connection_adapters/abstract/transaction.rb, line 610
      def rollback_transaction(transaction = nil)
        @connection.lock.synchronize do
          transaction ||= @stack.last
          begin
            transaction.rollback
          ensure
            @stack.pop if @stack.last == transaction
          end
          transaction.rollback_records
        end
      end