code: func (r *selectResult) NextRaw(ctx context.Context) ([]byte, error) {
  	re := <-r.results
  	r.partialCount++
  	r.feedback.Invalidate()
  	if re.result == nil || re.err != nil {
  		return nil, errors.Trace(re.err)
  	}
  	return re.result.GetData(), nil
  }
docs: // NextRaw returns the next raw partial result.