searchEngineClient.admin().indices().prepareRefresh(index).execute().actionGet();
                final long numOfDeleted = searchEngineClient.deleteByQuery(index, queryBuilder);
                logger.info("Deleted {} old docs.", numOfDeleted);
            } catch (final Exception e) {
                logger.error("Could not delete old docs at {}", dataConfig, e);

     *
     * @param index        the index name
     * @param queryBuilder the query to match documents for deletion
     * @return the number of documents deleted
     */
    public long deleteByQuery(final String index, final QueryBuilder queryBuilder) {

        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        SearchResponse response = client.prepareSearch(index)