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);
    }
  }
  /** Actually run the query */
  @Override
  public void process(ResponseBuilder rb) throws IOException {
    SolrQueryRequest req = rb.req;
    SolrQueryResponse rsp = rb.rsp;
    SolrParams params = req.getParams();
    if (!params.getBool(COMPONENT_NAME, true)) {
      return;
    }
    SolrIndexSearcher searcher = req.getSearcher();

    if (rb.getQueryCommand().getOffset() < 0) {
      throw new SolrException(
          SolrException.ErrorCode.BAD_REQUEST, "'start' parameter cannot be negative");
    }

    // -1 as flag if not set.
    long timeAllowed = (long) params.getInt(CommonParams.TIME_ALLOWED, -1);

    // Optional: This could also be implemented by the top-level searcher sending
    // a filter that lists the ids... that would be transparent to
    // the request handler, but would be more expensive (and would preserve score
    // too if desired).
    String ids = params.get(ShardParams.IDS);
    if (ids != null) {
      SchemaField idField = req.getSchema().getUniqueKeyField();
      List<String> idArr = StrUtils.splitSmart(ids, ",", true);
      int[] luceneIds = new int[idArr.size()];
      int docs = 0;
      for (int i = 0; i < idArr.size(); i++) {
        int id =
            req.getSearcher()
                .getFirstMatch(
                    new Term(idField.getName(), idField.getType().toInternal(idArr.get(i))));
        if (id >= 0) luceneIds[docs++] = id;
      }

      DocListAndSet res = new DocListAndSet();
      res.docList = new DocSlice(0, docs, luceneIds, null, docs, 0);
      if (rb.isNeedDocSet()) {
        List<Query> queries = new ArrayList<Query>();
        queries.add(rb.getQuery());
        List<Query> filters = rb.getFilters();
        if (filters != null) queries.addAll(filters);
        res.docSet = searcher.getDocSet(queries);
      }
      rb.setResults(res);
      rsp.add("response", rb.getResults().docList);
      return;
    }

    SolrIndexSearcher.QueryCommand cmd = rb.getQueryCommand();
    cmd.setTimeAllowed(timeAllowed);
    SolrIndexSearcher.QueryResult result = new SolrIndexSearcher.QueryResult();

    //
    // grouping / field collapsing
    //
    boolean doGroup = params.getBool(GroupParams.GROUP, false);
    if (doGroup) {
      try {
        cmd.groupCommands = new ArrayList<Grouping.Command>();

        String[] fields = params.getParams(GroupParams.GROUP_FIELD);
        String[] funcs = params.getParams(GroupParams.GROUP_FUNC);
        String[] queries = params.getParams(GroupParams.GROUP_QUERY);
        String groupSortStr = params.get(GroupParams.GROUP_SORT);
        Sort groupSort =
            groupSortStr != null ? QueryParsing.parseSort(groupSortStr, req.getSchema()) : null;

        int limitDefault = cmd.getLen(); // this is normally from "rows"
        int docsPerGroupDefault = params.getInt(GroupParams.GROUP_LIMIT, 1);

        // temporary: implement all group-by-field as group-by-func
        if (funcs == null) {
          funcs = fields;
        } else if (fields != null) {
          // catenate functions and fields
          String[] both = new String[fields.length + funcs.length];
          System.arraycopy(fields, 0, both, 0, fields.length);
          System.arraycopy(funcs, 0, both, fields.length, funcs.length);
          funcs = both;
        }

        if (funcs != null) {
          for (String groupByStr : funcs) {
            QParser parser = QParser.getParser(groupByStr, "func", rb.req);
            Query q = parser.getQuery();
            Grouping.CommandFunc gc = new Grouping.CommandFunc();
            gc.groupSort = groupSort;

            if (q instanceof FunctionQuery) {
              gc.groupBy = ((FunctionQuery) q).getValueSource();
            } else {
              gc.groupBy = new QueryValueSource(q, 0.0f);
            }
            gc.key = groupByStr;
            gc.groupLimit = limitDefault;
            gc.docsPerGroup = docsPerGroupDefault;

            cmd.groupCommands.add(gc);
          }
        }

        if (cmd.groupCommands.size() == 0) cmd.groupCommands = null;

        if (cmd.groupCommands != null) {
          if (rb.doHighlights || rb.isDebug()) {
            // we need a single list of the returned docs
            cmd.setFlags(SolrIndexSearcher.GET_DOCLIST);
          }

          searcher.search(result, cmd);
          rb.setResult(result);
          rsp.add("grouped", result.groupedResults);
          // TODO: get "hits" a different way to log
          return;
        }
      } catch (ParseException e) {
        throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, e);
      }
    }

    // normal search result
    searcher.search(result, cmd);
    rb.setResult(result);

    rsp.add("response", rb.getResults().docList);
    rsp.getToLog().add("hits", rb.getResults().docList.matches());

    doFieldSortValues(rb, searcher);
    doPrefetch(rb);
  }