materialize!

# File activerecord/lib/active_record/connection_adapters/abstract/transaction.rb, line 450
      def materialize!
        if joinable?
          if isolation_level
            connection.begin_isolated_db_transaction(isolation_level)
          else
            connection.begin_db_transaction
          end
        else
          connection.begin_deferred_transaction(isolation_level)
        end

        super
      end