code: func (b *builtinSysDateWithoutFspSig) evalTime(row chunk.Row) (d types.Time, isNull bool, err error) {
  	tz := b.ctx.GetSessionVars().Location()
  	now := time.Now().In(tz)
  	result, err := convertTimeToMysqlTime(now, 0, types.ModeHalfEven)
  	if err != nil {
  		return types.Time{}, true, err
  	}
  	return result, false, nil
  }
docs: // evalTime evals SYSDATE().
  // See https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_sysdate