ElasticSearch的基本用法与集群搭建(3)

// 获取少量数据100个
    private List<Integer> getSearchData(QueryBuilder queryBuilder) {
        List<Integer> ids = new ArrayList<>();
        SearchResponse searchResponse = client.prepareSearch(IndexName)
                .setTypes(TypeName).setQuery(queryBuilder).setSize(100)
                .execute().actionGet();
        SearchHits searchHits = searchResponse.getHits();
        for (SearchHit searchHit : searchHits) {
            Integer id = (Integer) searchHit.getSource().get("id");
            ids.add(id);
        }
        return ids;
    }

// 获取大量数据
    private List<Integer> getSearchDataByScrolls(QueryBuilder queryBuilder) {
        List<Integer> ids = new ArrayList<>();
        // 一次获取100000数据
        SearchResponse scrollResp = client.prepareSearch(IndexName)
                .setSearchType(SearchType.SCAN).setScroll(new TimeValue(60000))
                .setQuery(queryBuilder).setSize(100000).execute().actionGet();
        while (true) {
            for (SearchHit searchHit : scrollResp.getHits().getHits()) {
                Integer id = (Integer) searchHit.getSource().get(IDFieldName);
                ids.add(id);
            }
            scrollResp = client.prepareSearchScroll(scrollResp.getScrollId())
                    .setScroll(new TimeValue(600000)).execute().actionGet();
            if (scrollResp.getHits().getHits().length == 0) {
                break;
            }
        }

return ids;
    }

这里的QueryBuilder是一个查询条件，ES支持分页查询获取数据，也可以一次性获取大量数据，需要使用Scroll Search。

5、聚合（Aggregation Facet）查询

// 得到某段时间内设备列表上每个设备的数据分布情况<设备ID，数量>
    public Map<String, String> getDeviceDistributedInfo(String startTime,
            String endTime, List<String> deviceList) {

Map<String, String> resultsMap = new HashMap<>();

QueryBuilder deviceQueryBuilder = getDeviceQueryBuilder(deviceList);
        QueryBuilder rangeBuilder = getDateRangeQueryBuilder(startTime, endTime);
        QueryBuilder queryBuilder = QueryBuilders.boolQuery()
                .must(deviceQueryBuilder).must(rangeBuilder);

TermsBuilder termsBuilder = AggregationBuilders.terms("DeviceIDAgg").size(Integer.MAX_VALUE)
                .field(DeviceIDFieldName);
        SearchResponse searchResponse = client.prepareSearch(IndexName)
                .setQuery(queryBuilder).addAggregation(termsBuilder)
                .execute().actionGet();
        Terms terms = searchResponse.getAggregations().get("DeviceIDAgg");
        if (terms != null) {
            for (Terms.Bucket entry : terms.getBuckets()) {
                resultsMap.put(entry.getKey(),
                        String.valueOf(entry.getDocCount()));
            }
        }
        return resultsMap;
    }

Aggregation查询可以查询类似统计分析这样的功能：如某个月的数据分布情况，某类数据的最大、最小、总和、平均值等。