code: func (b *builtinNowWithArgSig) evalTime(row chunk.Row) (types.Time, bool, error) {
  	fsp, isNull, err := b.args[0].EvalInt(b.ctx, row)
  
  	if err != nil {
  		return types.Time{}, true, err
  	}
  
  	if isNull {
  		fsp = 0
  	} else if fsp > int64(types.MaxFsp) {
  		return types.Time{}, true, errors.Errorf("Too-big precision %v specified for 'now'. Maximum is %v.", fsp, types.MaxFsp)
  	} else if fsp < int64(types.MinFsp) {
  		return types.Time{}, true, errors.Errorf("Invalid negative %d specified, must in [0, 6].", fsp)
  	}
  
  	result, isNull, err := evalNowWithFsp(b.ctx, int(fsp))
  	return result, isNull, err
  }
docs: // evalTime evals NOW(fsp)
  // see: https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_now