code: func (m MDBXLog) Compare(xlog1, xlog2 xlog.Position) (int, error) {
  	if xlog1 == xlog2 {
  		return 0, nil
  	}
  	pos1, err := parseXlog(xlog1)
  	if err != nil {
  		return 0, err
  	}
  	pos2, err := parseXlog(xlog2)
  	if err != nil {
  		return 0, err
  	}
  	if pos1 > pos2 {
  		return 1, nil
  	}
  	return -1, nil
  }
docs: // Compare compares two xlog positions returning -1 if xlog1 < xlog2,
  // 0 if xlog1 == xlog2, and 1 if xlog1 > xlog2.