code: func convertNonInt2RoundUint64(sc *variable.StatementContext, x Datum) (d uint64, err error) {
  	decimalX, err := x.ToDecimal(sc)
  	if err != nil {
  		return d, errors.Trace(err)
  	}
  	d, err = decimal2RoundUint(decimalX)
  	if err != nil {
  		return d, errors.Trace(err)
  	}
  	return
  }
docs: // covertNonIntegerToUint64 coverts a non-integer to an uint64