new

# File activerecord/lib/active_record/connection_adapters/abstract/transaction.rb, line 388
      def initialize(connection, parent_transaction, **options)
        super(connection, **options)

        @parent = parent_transaction

        if isolation_level
          raise ActiveRecord::TransactionIsolationError, "cannot set transaction isolation in a nested transaction"
        end

        @parent.state.add_child(@state)
      end