.boostMode(CombineFunction.MULTIPLY));
            reader.addSort(SortBuilders.fieldSort(fessConfig.getIndexFieldClickCount()));
            reader.addSort(SortBuilders.scoreSort());
            return reader;
        }, docPerReq, () -> {
            systemHelper.calibrateCpuLoad();
            ThreadUtil.sleep(interval);
        }).then(response -> {
            refresh();

    protected SortBuilder<?> createFieldSortBuilder(final String field, final SortOrder order) {
        if (QueryFieldConfig.SCORE_FIELD.equals(field) || QueryFieldConfig.DOC_SCORE_FIELD.equals(field)) {
            return SortBuilders.scoreSort().order(order);
        }
        return SortBuilders.fieldSort(field).order(order);
    }

    /**
     * Checks if the specified field is a search field.
     * Uses O(1) Set lookup for improved performance.