code: func (b *builtinCurrentDateSig) evalTime(row chunk.Row) (d types.Time, isNull bool, err error) {
  	tz := b.ctx.GetSessionVars().Location()
  	var nowTs = &b.ctx.GetSessionVars().StmtCtx.NowTs
  	if nowTs.Equal(time.Time{}) {
  		*nowTs = time.Now()
  	}
  	year, month, day := nowTs.In(tz).Date()
  	result := types.Time{
  		Time: types.FromDate(year, int(month), day, 0, 0, 0, 0),
  		Type: mysql.TypeDate,
  		Fsp:  0}
  	return result, false, nil
  }
docs: // evalTime evals CURDATE().
  // See https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_curdate