java 通过聚合查询实现elasticsearch的group by后的数量

通过聚合查询获取group by 后的数量

/**
     * 获取key的个数
     *
     * @param key   要group by的字段名
     * @param index 索引名称
     * @return id的个数
     */
    public static int getkeycount(string key, string index) {
        int count = 0;
        transportclient client = null;
        try {
            client = connectionpool.getconnection();
            if (client == null) {
                throw new exception("没有获取到连接!");
            }
            searchrequestbuilder search = client.preparesearch(index);
            //cardinality聚合查询，相当于groupby字段名
            searchresponse sr = search.addaggregation(aggregationbuilders.cardinality(key + "_count").field(key)).execute().actionget();
            //从返回数据提取id总数
            cardinality result = sr.getaggregations().get(key + "_count");
            long value = result.getvalue();
            count = (int) value;
        } catch (interruptedexception e) {
        } catch (exception e) {
            logger.error("getkeycount错误", e);
        } finally {
            connectionpool.releaseconnection(client);
        }
        return count;
    }

获取group by后的所有key值

/**
     * 获取所有key
     *
     * @param key   被group by的字段名
     * @param index 索引名称
     * @return 所有id
     */
    public static list<string> getallkey(string key, string index) {
        int keycount = getkeycount(key, index);
        list<string> strings = new arraylist<>();
        transportclient client = null;
        try {
            client = connectionpool.getconnection();
            if (client == null) {
                throw new exception("没有获取到数据库连接!");
            }
            searchrequestbuilder searchrequestbuilder = client.preparesearch(index);
            //使用聚合，实现去重查询
            searchresponse searchresponse = searchrequestbuilder.
                    addaggregation(aggregationbuilders.terms("models").field(key).size(keycount)).execute().actionget();
            terms term = searchresponse.getaggregations().get("models");
            list<? extends terms.bucket> buckets = term.getbuckets();
            //遍历结果，提取出id
            for (terms.bucket bucket : buckets) {
                string keyasstring = bucket.getkeyasstring();
                strings.add(keyasstring);
            }
            buckets.clear();
        } catch (interruptedexception e) {

        } catch (exception e) {
            logger.error("getallkey错误", e);
        } finally {
            connectionpool.releaseconnection(client);
        }

        return strings;
    }

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