OpenSearch:Demo code for implementing iterative scroll queries

package com.aliyun.opensearch;

import com.aliyun.opensearch.sdk.dependencies.com.google.common.collect.Lists;
import com.aliyun.opensearch.sdk.generated.OpenSearch;
import com.aliyun.opensearch.sdk.generated.search.*;
import com.aliyun.opensearch.search.DeepPageingIterator;
import java.nio.charset.Charset;

public class testScrollIterator {

    // Replace these values with your actual OpenSearch application details.
    private static String appName = "<your-app-name>";
    private static String tableName = "<your-table-name>";
    private static String host = "<your-opensearch-api-endpoint>";

    public static void main(String[] args) {

        // Read credentials from environment variables — never hardcode them.
        String accesskey = System.getenv("ALIBABA_CLOUD_ACCESS_KEY_ID");
        String secret = System.getenv("ALIBABA_CLOUD_ACCESS_KEY_SECRET");

        // Log the file encoding for debugging purposes.
        System.out.println(String.format("file.encoding: %s", System.getProperty("file.encoding")));
        System.out.println(String.format("defaultCharset: %s", Charset.defaultCharset().name()));

        // Initialize the client chain: OpenSearch → OpenSearchClient → SearcherClient.
        OpenSearch openSearch = new OpenSearch(accesskey, secret, host);
        OpenSearchClient serviceClient = new OpenSearchClient(openSearch);
        SearcherClient searcherClient = new SearcherClient(serviceClient);

        // Configure the config clause: application name, page size, response format, and fetch fields.
        Config config = new Config(Lists.newArrayList(appName));
        config.setStart(0);       // Has no effect in scroll queries; the default value 0 is always used.
        config.setHits(5);        // Number of documents per page.
        config.setSearchFormat(SearchFormat.FULLJSON);  // Supported formats: JSON and FULLJSON.
        config.setFetchFields(Lists.newArrayList("id", "name", "phone", "int_arr", "literal_arr", "float_arr", "cate_id"));

        // Build the search query. Specifying multiple index fields in separate setQuery calls
        // overwrites the previous query — include all index fields in a single setQuery call.
        SearchParams searchParams = new SearchParams(config);
        searchParams.setQuery("name:'opensearch'");

        // Optional: add a filter condition.
        // searchParams.setFilter("cate_id<=3");

        // Scroll queries support sorting on a single field only.
        Sort sorter = new Sort();
        sorter.addToSortFields(new SortField("id", Order.DECREASE));
        searchParams.setSort(sorter);

        // Enable deep paging.
        DeepPaging deep = new DeepPaging();
        searchParams.setDeepPaging(deep);

        // DeepPageingIterator manages scroll IDs automatically — no manual tracking needed.
        DeepPageingIterator pagesIterator = new DeepPageingIterator(searcherClient, searchParams);

        // Optional: set a custom iteration interval in milliseconds (default: 100 ms).
        // Increase this value to reduce pressure on the OpenSearch service.
        // pagesIterator.setPagingIntervals(80);

        // Check for errors using the error code and message, not the status field.
        try {
            System.out.println("Starting iterative scroll query...");
            while (pagesIterator.hasNext()) {
                System.out.println(pagesIterator.next());
            }
        } catch (Exception ex) {
            System.out.println("Error: " + ex.getMessage());
        }
    }
}

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