@Override
    public E next() {
      if (next_pointer >= 0) {
        pointer = next_pointer;
      }
      else {
        pointer = getNextIndex(pointer);
        if (pointer == -1) {
          pointer = size;
        }
      }

      next_pointer = -1;
      return pointer < size ? colValuesInternal.getKey(pointer) : null;
    }
@Override
    public E next()