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Java使用ES?Client?調(diào)用滾動查詢及Elasticsearch滾動查詢Scrolling機制

更新時間：2023年08月14日 10:30:26 作者：周全全

Elasticsearch提供了一種稱為"滾動查詢"（Scrolling）的機制，用于處理大型數(shù)據(jù)集的分頁查詢，這篇文章給大家介紹滾動查詢的一般步驟及Java使用ESClient調(diào)用滾動查詢的方法，感興趣的朋友一起看看吧

Elasticsearch"滾動查詢"（Scrolling）的機制的與Java使用ES Client 調(diào)用滾動查詢

前言

ES在進行普通的查詢時，默認只會查詢出來10條數(shù)據(jù)。我們通過設(shè)置es中的size可以將最終的查詢結(jié)果從10增加到10000。如果需要查詢數(shù)據(jù)量大于es的翻頁限制或者需要將es的數(shù)據(jù)進行導(dǎo)出又當(dāng)如何？
Elasticsearch提供了一種稱為"滾動查詢"（Scrolling）的機制，用于處理大型數(shù)據(jù)集的分頁查詢。滾動查詢允許在持續(xù)的時間段內(nèi)保持一個活動的搜索上下文，然后使用滾動ID進行迭代檢索結(jié)果。滾動查詢和關(guān)系型數(shù)據(jù)庫中的游標(biāo)有點類似，因此也叫游標(biāo)查詢

1. 滾動查詢的一般步驟

1.1 發(fā)起初始搜索請求,返回命中結(jié)果和滾動ID

scroll=5m表示每個滾動查詢的有效時間為5分鐘

POST /your_index/_search?scroll=5m
{
  "size": 100,       // 每次返回的結(jié)果數(shù)量
  "query": { ... }   // 查詢條件
}

命中結(jié)果：

{
"_scroll_id": "DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAAAD4WYm9laVYtZndUQlNsdDcwakFMNjU1QQ==",
"hits": {
"total": {
"value": 10000,
"relation": "eq"
},
"hits": [ ... ] // 檢索到的文檔
}
}

示例：

在這里插入圖片描述

1.2 使用滾動ID檢索下一頁結(jié)果

POST /_search/scroll
{
  "scroll": "5m",
  "scroll_id": "DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAAAD4WYm9laVYtZndUQlNsdDcwakFMNjU1QQ=="
}

示例：

POST /_search/scroll
 {
   "scroll": "5m",
   "scroll_id": "FGluY2x1ZGVfY29udGV4dF91dWlkDXF1ZXJ5QW5kRmV0Y2gBFDJPRXc0WWdCY1BLWlo1MTk4MmR3AAAAAAAAAXYWcWgwSW5CQUtScEd2T2QtRGtYaWliQQ=="
 }

1.4 重復(fù)執(zhí)行直到?jīng)]有檢索結(jié)果返回

Elasticsearch將返回下一頁結(jié)果和一個新的滾動ID?？梢愿鶕?jù)需要重復(fù)這個步驟，直到?jīng)]有更多結(jié)果為止

1.5 清除滾動上下文釋放資源

滾動查詢結(jié)束后，您可以通過發(fā)送一個清除滾動上下文的請求來釋放資源：

DELETE /_search/scroll
{
  "scroll_id": [
    "DXF1ZXJ5QW5kRmV0Y2gBAAAAAAAAAD4WYm9laVYtZndUQlNsdDcwakFMNjU1QQ=="
  ]
}

以上為滾動查詢進行分頁檢索的基本過程。在每個滾動請求中，都需要提供先前滾動請求返回的滾動ID。這樣Elasticsearch才能夠維護搜索上下文并返回正確的結(jié)果

2.Java Elasticsearch客戶端執(zhí)行滾動查詢

public static void main(String[] args) {
    long start = System.currentTimeMillis();
    //構(gòu)建es HttpHost對象
    HttpHost httpHost1 = new HttpHost("192.168.1.1", 9200, "http");
    // 滾動時間窗口
    long scrollTime = 1L;
    // 每次返回的文檔數(shù)量
    int batchSize = 20000;
    //索引名
    String indexName = "你的索引名稱";
    try (RestHighLevelClient client = new RestHighLevelClient(RestClient.builder(httpHost1))) {
        //構(gòu)建查詢請求
        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
        searchSourceBuilder.query(QueryBuilders.boolQuery());
        searchSourceBuilder.size(batchSize);
        //設(shè)置查詢返回字段
        String[] includes = {};
        searchSourceBuilder.fetchSource(includes, null);
        // 滾動查詢請求
        SearchRequest searchRequest = new SearchRequest(indexName);
        searchRequest.source(searchSourceBuilder);
        //設(shè)置請求滾動時間窗口時間
        searchRequest.scroll(TimeValue.timeValueMinutes(scrollTime));
        //執(zhí)行首次檢索
        SearchResponse searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);
        //首次檢索返回scrollId，用于下一次的滾動查詢
        String scrollId = searchResponse.getScrollId();
        //獲取首次檢索命中結(jié)果
        SearchHit[] searchHits = searchResponse.getHits().getHits();
        //計數(shù)
        int count = 0;
        // 處理第一批結(jié)果
        for (SearchHit hit : searchHits) {
            // 處理單個文檔
            JSONObject dataJson = (JSONObject) JSON.parse(hit.getSourceAsString());
            System.out.println("====對首次請求的進行處理，當(dāng)前計數(shù)：" + count++);
        }
        // 處理滾動結(jié)果
        while (searchHits != null && searchHits.length > 0) {
            SearchScrollRequest scrollRequest = new SearchScrollRequest(scrollId);
            scrollRequest.scroll(TimeValue.timeValueMinutes(scrollTime));
            searchResponse = client.scroll(scrollRequest, RequestOptions.DEFAULT);
            scrollId = searchResponse.getScrollId();
            searchHits = searchResponse.getHits().getHits();
            for (SearchHit hit : searchHits) {
                JSONObject dataJson = (JSONObject) JSON.parse(hit.getSourceAsString());
                System.out.println("====滾動查詢，當(dāng)前計數(shù)：" + count++);
            }
        }
        // 清理滾動上下文
        ClearScrollRequest clearScrollRequest = new ClearScrollRequest();
        clearScrollRequest.addScrollId(scrollId);
        ClearScrollResponse clearScrollResponse = client.clearScroll(clearScrollRequest, RequestOptions.DEFAULT);
        boolean succeeded = clearScrollResponse.isSucceeded();
        long end = System.currentTimeMillis();
        System.out.println("共執(zhí)行時間：" + (end - start) / 1000 + " s");
    } catch (Exception e) {
        System.out.println("===error==" + e.getMessage());
        e.printStackTrace();
    }
}

3. SpringDataElasticsearch滾動查詢

import org.elasticsearch.action.search .*;
import org.elasticsearch.client .*;
import org.elasticsearch.common.unit .*;
import org.elasticsearch.index.query .*;
import org.elasticsearch.search .*;
import org.elasticsearch.search.builder .*;
import org.springframework.beans.factory.annotation .*;
import org.springframework.data.elasticsearch.core .*;
import org.springframework.data.elasticsearch.core.query .*;
public class ScrollSearchExample {
    @Autowired
    private ElasticsearchOperations elasticsearchOperations;
    public void performScrollSearch() {
        String scrollTime = "1m";  // 滾動時間窗口
        int batchSize = 100;  // 每次返回的文檔數(shù)量
        QueryBuilder queryBuilder = QueryBuilders.matchQuery("field", "value");
        NativeSearchQueryBuilder searchQuery = new NativeSearchQueryBuilder();
        searchQuery.withQuery(queryBuilder).withPageable(PageRequest.of(0, batchSize)).build();
        SearchResponse searchResponse = elasticsearchOperations.startScroll(
                scrollTime,
                searchQuery,
                YourEntityClass.class,
                IndexCoordinates.of("your_index")
        );
        String scrollId = searchResponse.getScrollId();
        SearchHits<YourEntityClass> searchHits = searchResponse.getSearchHits();
        // 處理第一批結(jié)果
        for (SearchHit<YourEntityClass> hit : searchHits) {
            YourEntityClass entity = hit.getContent();
            // 處理單個文檔
        }
        // 處理滾動結(jié)果
        while (searchHits != null && searchHits.hasSearchHits()) {
            searchResponse = elasticsearchOperations.continueScroll(scrollId, scrollTime, YourEntityClass.class);
            scrollId = searchResponse.getScrollId();
            searchHits = searchResponse.getSearchHits();
            for (SearchHit<YourEntityClass> hit : searchHits) {
                YourEntityClass entity = hit.getContent();
                // 處理單個文檔
            }
        }
        // 清理滾動上下文
        elasticsearchOperations.clearScroll(scrollId);
    }
}

到此這篇關(guān)于Java使用ES Client 調(diào)用滾動查詢及Elasticsearch滾動查詢Scrolling機制的文章就介紹到這了,更多相關(guān)java Elasticsearch滾動查詢內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

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