code: func DecodeRowKey(key kv.Key) (int64, error) {
  	if len(key) != recordRowKeyLen || !hasTablePrefix(key) || !hasRecordPrefixSep(key[prefixLen-2:]) {
  		return 0, errInvalidKey.GenWithStack("invalid key - %q", key)
  	}
  	u := binary.BigEndian.Uint64(key[prefixLen:])
  	return codec.DecodeCmpUintToInt(u), nil
  }
docs: // DecodeRowKey decodes the key and gets the handle.