code: private void pessimisticGetNext(
                                     DeleteStack    stack)
      {
          synchronized(_index)
          {
              internalGetNext(stack, _index.vno(), _index.xno());
              _pessimisticGetNexts++;
          }
      }
docs: Get the next key pessimistically.
  
  <p>Lock the whole index and call internalGetNext().</p>
  
  @param stack The stack used to record the traversal.