flist.toArray(new FunctionScoreQueryBuilder.FilterFunctionBuilder[flist.size()]))
                    .boostMode(CombineFunction.MULTIPLY));
            reader.addSort(SortBuilders.fieldSort(fessConfig.getIndexFieldClickCount()));
            reader.addSort(SortBuilders.scoreSort());
            return reader;
        }, docPerReq, () -> {
            systemHelper.calibrateCpuLoad();
            ThreadUtil.sleep(interval);

        // set query.
        final QueryBuilder q = buildQuery(query, fields);

        // set function score
        final QueryBuilder queryBuilder = buildFunctionScoreQuery(query, q);
        builder.addSort("_score", SortOrder.DESC);

        // set filter query.
        final List<QueryBuilder> filterList = new ArrayList<>(10);
        if (!tags.isEmpty()) {

                builder.setQuery(QueryBuilders.matchAllQuery());
            }
            if (sortBuilders != null) {
                for (SortBuilder<?> sortBuilder : sortBuilders) {
                    builder.addSort(sortBuilder);
                }
            }
            if (from != null) {
                builder.setFrom(from);
            }
            if (size != null) {
                builder.setSize(size);