code: func (e *evalContext) decodeRelatedColumnVals(relatedColOffsets []int, value [][]byte, row []types.Datum) error {
  	var err error
  	for _, offset := range relatedColOffsets {
  		row[offset], err = tablecodec.DecodeColumnValue(value[offset], e.fieldTps[offset], e.sc.TimeZone)
  		if err != nil {
  			return errors.Trace(err)
  		}
  	}
  	return nil
  }
docs: // decodeRelatedColumnVals decodes data to Datum slice according to the row information.