final FessConfig fessConfig = ComponentUtil.getFessConfig();

        final StringBuilder resultBuf = new StringBuilder();

        // clean up
        final QueryBuilder queryBuilder = QueryBuilders.rangeQuery(fessConfig.getIndexFieldExpires()).to("now");
        try {
            searchEngineClient.deleteByQuery(fessConfig.getIndexDocumentUpdateIndex(), queryBuilder);

        } catch (final Exception e) {