* @return the number of documents that were deleted
     */
    protected long deleteByQueryBuilder(final SearchEngineClient searchEngineClient, final String index, final QueryBuilder queryBuilder) {
        refreshIndex(searchEngineClient, index);
        final long numOfDeleted = searchEngineClient.deleteByQuery(index, queryBuilder);
        if (logger.isDebugEnabled()) {
            logger.debug("Deleted {} stale documents.", numOfDeleted);

                    final FessConfig fessConfig) {
                return documentSizeByQuery;
            }

            @Override
            protected int refreshIndex(final SearchEngineClient searchEngineClient, final String index) {
                return 200;
            }
        };
        indexingHelper.setMaxRetryCount(5);
        indexingHelper.setDefaultRowSize(100);