Elasticsearch Java API 的使用（8）—Scroll (游标)API详解

####滚动查询
Elasticsearch中进行大数据量查询时，往往因为设备、网络传输问题影响查询数据的效率；Elasticsearch中提供了 Scroll（游标）的方式对数据进行少量多批次的滚动查询，来提高查询效率。

public class Scroll {

    public static void main(String[] args) {

        try{
            long startTime = System.currentTimeMillis();
            /*创建客户端*/
            //client startup
            //设置集群名称
            Settings settings = Settings.builder()
                    .put("cluster.name", "elsearch")
                    .put("client.transport.sniff", true)
                    .build();
            //创建client
            TransportClient client = new PreBuiltTransportClient(settings)
                    .addTransportAddress(new InetSocketTransportAddress(
                    InetAddress.getByName("54.223.232.95"),9300));

            List<String> result = new ArrayList<>();

            String scrollId = "";

            //第一次请求
            SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();


            //TODO: 设置查询条件
            RangeQueryBuilder rangequerybuilder = QueryBuilders
                .rangeQuery("inputtime")
                .from("2016-12-14 02:00:00").to("2016-12-14 07:59:59");
            sourceBuilder.query(QueryBuilders.boolQuery()
                .must(QueryBuilders
                        .matchPhraseQuery("pointid","W3.UNIT1.10HFC01CT013"))
                    .must(rangequerybuilder))
                    .size(100)//如果开启游标，则滚动获取
                    .sort("inputtime", SortOrder.ASC);
            //查询
            SearchRequest request = Requests.searchRequest("pointdata");
                request.scroll("2m");
                request.source(sourceBuilder);
            SearchResponse response = client.search(request).actionGet();
            //TODO:处理数据
            SearchHits hits = response.getHits();
            for(int i = 0; i < hits.getHits().length; i++) {
                //System.out.println(hits.getHits()[i].getSourceAsString());
                result.add(hits.getHits()[i].getSourceAsString());
            }
            //记录滚动ID
            scrollId = response.getScrollId();


            while(true){
                //后续的请求
                //scrollId = query.getScollId();
                SearchScrollRequestBuilder searchScrollRequestBuilder = client
                    .prepareSearchScroll(scrollId);            
                // 重新设定滚动时间            
                //TimeValue timeValue = new TimeValue(30000);
                searchScrollRequestBuilder.setScroll("2m");
                // 请求            
                SearchResponse response1 = searchScrollRequestBuilder.get();

                //TODO:处理数据
                SearchHits hits2 = response1.getHits();
                if(hits2.getHits().length == 0){
                    break;
                }
                for(int i = 0; i < hits2.getHits().length; i++) {
                    result.add(hits2.getHits()[i].getSourceAsString());
                }
                //下一批处理
                scrollId = response1.getScrollId();
            }

            System.out.println(result.size());
            long endTime = System.currentTimeMillis();
            System.out.println("Java程序运行时间：" + (endTime - startTime) + "ms");
        }catch(Exception e){
            e.printStackTrace();
        }

    }

Scroll原理查看：Elasticsearch 使用scroll滚动技术实现大数据量搜索