code: func (f *fragment) unprotectedRow(rowID uint64) *Row {
  	r, ok := f.rowCache.Fetch(rowID)
  	if ok && r != nil {
  		return r
  	}
  
  	row := f.rowFromStorage(rowID)
  	f.rowCache.Add(rowID, row)
  	return row
  }
docs: // unprotectedRow returns a row from the row cache if available or from storage
  // (updating the cache).