public static long scroll(final String index, final Function<SearchHit, Boolean> callback) {
        final SearchEngineClient client = ComponentUtil.getSearchEngineClient();
        return client.<SearchHit> scrollSearch(index, searchRequestBuilder -> true, (searchResponse, hit) -> hit,
                hit -> callback.apply(hit));
    }

    public static String getXContentString(final ToXContent xContent, final MediaType mediaType) {
        try {

                searchEngineClient.getDocumentList(fessConfig.getIndexDocumentSearchIndex(), searchRequestBuilder -> {
                    searchRequestBuilder.setQuery(
                            QueryBuilders.termsQuery(docIdField, deleteFileMap.keySet().toArray(new String[deleteFileMap.size()])));
                    searchRequestBuilder.setFetchSource(new String[] { docIdField }, StringUtil.EMPTY_STRINGS);
                    return true;

import org.codelibs.fess.suggest.exception.SuggesterException;
import org.codelibs.fess.suggest.normalizer.Normalizer;
import org.codelibs.fess.suggest.request.Request;
import org.opensearch.action.search.SearchRequestBuilder;
import org.opensearch.action.search.SearchResponse;
import org.opensearch.client.Client;
import org.opensearch.common.lucene.search.function.CombineFunction;

import org.codelibs.fess.util.ComponentUtil;
import org.codelibs.fess.util.DocList;
import org.codelibs.fess.util.MemoryUtil;
import org.codelibs.fess.util.ThreadDumpUtil;
import org.opensearch.action.search.SearchRequestBuilder;
import org.opensearch.index.query.QueryBuilder;
import org.opensearch.index.query.QueryBuilders;
import org.opensearch.search.sort.SortOrder;

public class IndexUpdater extends Thread {

        client.search(request, listener);
    }

    @Override
    public SearchRequestBuilder prepareSearch(final String... indices) {
        final SearchRequestBuilder builder = client.prepareSearch(indices);
        if (searchPreference != null) {
            builder.setPreference(searchPreference);
        }
        return builder;
    }