private void doHighlightingByFastVectorHighlighter(
     FastVectorHighlighter highlighter,
     FieldQuery fieldQuery,
     SolrQueryRequest req,
     NamedList docSummaries,
     int docId,
     Document doc,
     String fieldName)
     throws IOException {
   SolrParams params = req.getParams();
   SolrFragmentsBuilder solrFb = getSolrFragmentsBuilder(fieldName, params);
   String[] snippets =
       highlighter.getBestFragments(
           fieldQuery,
           req.getSearcher().getIndexReader(),
           docId,
           fieldName,
           params.getFieldInt(fieldName, HighlightParams.FRAGSIZE, 100),
           params.getFieldInt(fieldName, HighlightParams.SNIPPETS, 1),
           getFragListBuilder(fieldName, params),
           getFragmentsBuilder(fieldName, params),
           solrFb.getPreTags(params, fieldName),
           solrFb.getPostTags(params, fieldName),
           getEncoder(fieldName, params));
   if (snippets != null && snippets.length > 0) docSummaries.add(fieldName, snippets);
   else alternateField(docSummaries, params, doc, fieldName);
 }