public int getCount(final Consumer<SearchRequestBuilder> callback) {
        final TotalHits totalHits = getClient().get(c -> {
            final SearchRequestBuilder builder = c.prepareSearch(index).setSize(0).setTrackTotalHits(true);
            callback.accept(builder);
            return builder.execute();
        }).getHits().getTotalHits();
        return totalHits != null ? (int) totalHits.value : 0;
    }