begin_transaction

# File activerecord/lib/active_record/connection_adapters/abstract/transaction.rb, line 163
      def begin_transaction(options = {})
        transaction =
          if @stack.empty?
            RealTransaction.new(@connection, options)
          else
            SavepointTransaction.new(@connection, "active_record_#{@stack.size}", options)
          end
        @stack.push(transaction)
        transaction
      end