code: func (s *ScrollService) bodyFirst() (interface{}, error) {
  	var err error
  	var body interface{}
  
  	if s.body != nil {
  		body = s.body
  	} else {
  		// Use _doc sort by default if none is specified
  		if !s.ss.hasSort() {
  			// Use efficient sorting when no user-defined query/body is specified
  			s.ss = s.ss.SortBy(SortByDoc{})
  		}
  
  		// Body from search source
  		body, err = s.ss.Source()
  		if err != nil {
  			return nil, err
  		}
  	}
  
  	return body, nil
  }
docs: // bodyFirst returns the request to fetch the first batch of results.