public void handleMergeFields(ResponseBuilder rb, SolrIndexSearcher searcher)
        throws IOException {
      SolrQueryRequest req = rb.req;
      SolrQueryResponse rsp = rb.rsp;
      // The query cache doesn't currently store sort field values, and SolrIndexSearcher doesn't
      // currently have an option to return sort field values.  Because of this, we
      // take the documents given and re-derive the sort values.
      //
      // TODO: See SOLR-5595
      boolean fsv = req.getParams().getBool(ResponseBuilder.FIELD_SORT_VALUES, false);
      if (fsv) {
        NamedList<Object[]> sortVals = new NamedList<>(); // order is important for the sort fields
        IndexReaderContext topReaderContext = searcher.getTopReaderContext();
        List<LeafReaderContext> leaves = topReaderContext.leaves();
        LeafReaderContext currentLeaf = null;
        if (leaves.size() == 1) {
          // if there is a single segment, use that subReader and avoid looking up each time
          currentLeaf = leaves.get(0);
          leaves = null;
        }

        DocList docList = rb.getResults().docList;

        // sort ids from lowest to highest so we can access them in order
        int nDocs = docList.size();
        final long[] sortedIds = new long[nDocs];
        final float[] scores = new float[nDocs]; // doc scores, parallel to sortedIds
        DocList docs = rb.getResults().docList;
        DocIterator it = docs.iterator();
        for (int i = 0; i < nDocs; i++) {
          sortedIds[i] = (((long) it.nextDoc()) << 32) | i;
          scores[i] = docs.hasScores() ? it.score() : Float.NaN;
        }

        // sort ids and scores together
        new InPlaceMergeSorter() {
          @Override
          protected void swap(int i, int j) {
            long tmpId = sortedIds[i];
            float tmpScore = scores[i];
            sortedIds[i] = sortedIds[j];
            scores[i] = scores[j];
            sortedIds[j] = tmpId;
            scores[j] = tmpScore;
          }

          @Override
          protected int compare(int i, int j) {
            return Long.compare(sortedIds[i], sortedIds[j]);
          }
        }.sort(0, sortedIds.length);

        SortSpec sortSpec = rb.getSortSpec();
        Sort sort = searcher.weightSort(sortSpec.getSort());
        SortField[] sortFields =
            sort == null ? new SortField[] {SortField.FIELD_SCORE} : sort.getSort();
        List<SchemaField> schemaFields = sortSpec.getSchemaFields();

        for (int fld = 0; fld < schemaFields.size(); fld++) {
          SchemaField schemaField = schemaFields.get(fld);
          FieldType ft = null == schemaField ? null : schemaField.getType();
          SortField sortField = sortFields[fld];

          SortField.Type type = sortField.getType();
          // :TODO: would be simpler to always serialize every position of SortField[]
          if (type == SortField.Type.SCORE || type == SortField.Type.DOC) continue;

          FieldComparator<?> comparator = null;
          LeafFieldComparator leafComparator = null;
          Object[] vals = new Object[nDocs];

          int lastIdx = -1;
          int idx = 0;

          for (int i = 0; i < sortedIds.length; ++i) {
            long idAndPos = sortedIds[i];
            float score = scores[i];
            int doc = (int) (idAndPos >>> 32);
            int position = (int) idAndPos;

            if (leaves != null) {
              idx = ReaderUtil.subIndex(doc, leaves);
              currentLeaf = leaves.get(idx);
              if (idx != lastIdx) {
                // we switched segments.  invalidate comparator.
                comparator = null;
              }
            }

            if (comparator == null) {
              comparator = sortField.getComparator(1, 0);
              leafComparator = comparator.getLeafComparator(currentLeaf);
            }

            doc -= currentLeaf.docBase; // adjust for what segment this is in
            leafComparator.setScorer(new FakeScorer(doc, score));
            leafComparator.copy(0, doc);
            Object val = comparator.value(0);
            if (null != ft) val = ft.marshalSortValue(val);
            vals[position] = val;
          }

          sortVals.add(sortField.getField(), vals);
        }

        rsp.add("merge_values", sortVals);
      }
    }
  protected void doFieldSortValues(ResponseBuilder rb, SolrIndexSearcher searcher)
      throws IOException {
    SolrQueryRequest req = rb.req;
    SolrQueryResponse rsp = rb.rsp;

    // The query cache doesn't currently store sort field values, and SolrIndexSearcher doesn't
    // currently have an option to return sort field values.  Because of this, we
    // take the documents given and re-derive the sort values.
    boolean fsv = req.getParams().getBool(ResponseBuilder.FIELD_SORT_VALUES, false);
    if (fsv) {
      Sort sort = rb.getSortSpec().getSort();
      SortField[] sortFields =
          sort == null ? new SortField[] {SortField.FIELD_SCORE} : sort.getSort();
      NamedList sortVals = new NamedList(); // order is important for the sort fields
      Field field = new Field("dummy", "", Field.Store.YES, Field.Index.NO); // a dummy Field

      SolrIndexReader reader = searcher.getReader();
      SolrIndexReader[] readers = reader.getLeafReaders();
      SolrIndexReader subReader = reader;
      if (readers.length == 1) {
        // if there is a single segment, use that subReader and avoid looking up each time
        subReader = readers[0];
        readers = null;
      }
      int[] offsets = reader.getLeafOffsets();

      for (SortField sortField : sortFields) {
        int type = sortField.getType();
        if (type == SortField.SCORE || type == SortField.DOC) continue;

        FieldComparator comparator = null;
        FieldComparator comparators[] =
            (readers == null) ? null : new FieldComparator[readers.length];

        String fieldname = sortField.getField();
        FieldType ft = fieldname == null ? null : req.getSchema().getFieldTypeNoEx(fieldname);

        DocList docList = rb.getResults().docList;
        ArrayList<Object> vals = new ArrayList<Object>(docList.size());
        DocIterator it = rb.getResults().docList.iterator();

        int offset = 0;
        int idx = 0;

        while (it.hasNext()) {
          int doc = it.nextDoc();
          if (readers != null) {
            idx = SolrIndexReader.readerIndex(doc, offsets);
            subReader = readers[idx];
            offset = offsets[idx];
            comparator = comparators[idx];
          }

          if (comparator == null) {
            comparator = sortField.getComparator(1, 0);
            comparator = comparator.setNextReader(subReader, offset);
            if (comparators != null) comparators[idx] = comparator;
          }

          doc -= offset; // adjust for what segment this is in
          comparator.copy(0, doc);
          Object val = comparator.value(0);

          // Sortable float, double, int, long types all just use a string
          // comparator. For these, we need to put the type into a readable
          // format.  One reason for this is that XML can't represent all
          // string values (or even all unicode code points).
          // indexedToReadable() should be a no-op and should
          // thus be harmless anyway (for all current ways anyway)
          if (val instanceof String) {
            field.setValue((String) val);
            val = ft.toObject(field);
          }

          // Must do the same conversion when sorting by a
          // String field in Lucene, which returns the terms
          // data as BytesRef:
          if (val instanceof BytesRef) {
            field.setValue(((BytesRef) val).utf8ToString());
            val = ft.toObject(field);
          }

          vals.add(val);
        }

        sortVals.add(fieldname, vals);
      }

      rsp.add("sort_values", sortVals);
    }
  }
 @Override
 public Object value(int slot) {
   return wrappedComparator.value(slot);
 }