ElasticSearch High Level REST API【3】Scroll 滚屏

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ES中提供了 FROM/SIZE 分页，但这种分页有性能瓶颈。

Scroll会以间隔时间滚屏的方式返回全部的查询数据，可以作为数据量很大的情况下，分页的一个替代方案

完整的示例如下：

public void scroll(){

        RestHighLevelClient client = elasticClient.getRestHighLevelClient();

        //初始化scroll

        final Scroll scroll = new Scroll(TimeValue.timeValueMinutes(1L)); //设定滚动时间间隔

        SearchRequest searchRequest = new SearchRequest();

        searchRequest.scroll(scroll);

        SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();

        searchSourceBuilder.query(matchAllQuery());

        searchSourceBuilder.size(5); //设定每次返回多少条数据

        searchRequest.source(searchSourceBuilder);

        SearchResponse searchResponse = null;

        try {

            searchResponse = client.search(searchRequest, RequestOptions.DEFAULT);

        } catch (IOException e) {

            e.printStackTrace();

        }

        String scrollId = searchResponse.getScrollId();

        SearchHit[] searchHits = searchResponse.getHits().getHits();

        System.out.println("-----首页-----");

        for (SearchHit searchHit : searchHits) {

            System.out.println(searchHit.getSourceAsString());

        }

        //遍历搜索命中的数据，直到没有数据

        while (searchHits != null && searchHits.length > 0) {

            SearchScrollRequest scrollRequest = new SearchScrollRequest(scrollId);

            scrollRequest.scroll(scroll);

            try {

                searchResponse = client.scroll(scrollRequest, RequestOptions.DEFAULT);

            } catch (IOException e) {

                e.printStackTrace();

            }

            scrollId = searchResponse.getScrollId();

            searchHits = searchResponse.getHits().getHits();

            if (searchHits != null && searchHits.length > 0) {

                System.out.println("-----下一页-----");

                for (SearchHit searchHit : searchHits) {

                    System.out.println(searchHit.getSourceAsString());

                }

            }

        }

        //清除滚屏

        ClearScrollRequest clearScrollRequest = new ClearScrollRequest();

        clearScrollRequest.addScrollId(scrollId);//也可以选择setScrollIds()将多个scrollId一起使用

        ClearScrollResponse clearScrollResponse = null;

        try {

            clearScrollResponse = client.clearScroll(clearScrollRequest,RequestOptions.DEFAULT);

        } catch (IOException e) {

            e.printStackTrace();

        }

        boolean succeeded = clearScrollResponse.isSucceeded();

        System.out.println("succeeded:" + succeeded);

    }