code: func (b *builtinUUIDSig) evalString(_ chunk.Row) (d string, isNull bool, err error) {
  	return uuid.NewV1().String(), false, nil
  }
docs: // evalString evals a builtinUUIDSig.
  // See https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_uuid