code: func (e *ReplaceExec) removeIndexRow(r toBeCheckedRow) (bool, bool, error) {
  	for _, uk := range r.uniqueKeys {
  		if val, found := e.dupKVs[string(uk.newKV.key)]; found {
  			handle, err := tables.DecodeHandle(val)
  			if err != nil {
  				return false, found, err
  			}
  			rowUnchanged, err := e.removeRow(handle, r)
  			if err != nil {
  				return false, found, err
  			}
  			return rowUnchanged, found, nil
  		}
  	}
  	return false, false, nil
  }
docs: // removeIndexRow removes the row which has a duplicated key.
  // the return values:
  //     1. bool: true when the row is unchanged. This means no need to remove, and then add the row.
  //     2. bool: true when found the duplicated key. This only means that duplicated key was found,
  //              and the row was removed.
  //     3. error: the error.