SpringBoot - Elasticsearch Rest Client使用详解3（聚合统计、获取所有分组数据）
作者：hangge | 2024-12-18 08:38
Elasticsearch 中可以实现基于字段进行分组聚合的统计，聚合操作支持 count(）、sum(）、avg(）、max(）、min() 等。本文通过样例分别进行演示。
五、aggregations 聚合统计
1，count 聚合（统计相同年龄的学员个数）
（1）假设我们需要统计相同年龄的学员个数，首先调用 Elasticsearch 的 API 接口添加一些初始数据：
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/1' -d'{"name":"tom","age":18}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/2' -d'{"name":"jack","age":29}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/3' -d'{"name":"jessica","age":18}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/4' -d'{"name":"dave","age":19}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/5' -d'{"name":"lilei","age":18}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/6' -d'{"name":"lili","age":29}'
（2）下面是聚合统计样例代码，统计相同年龄的学员个数：
//获取 RestClient 连接
RestHighLevelClient client = new RestHighLevelClient(
RestClient.builder(
new HttpHost("192.168.121.128", 9200, "http"),
new HttpHost("192.168.121.129", 9200, "http"),
new HttpHost("192.168.121.130", 9200, "http")));
SearchRequest searchRequest = new SearchRequest();
searchRequest.indices("stu");
//指定查询条件
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
//指定分组信息，默认是执行 count 聚合
TermsAggregationBuilder aggregation = AggregationBuilders.terms("age_term")
.field("age");
searchSourceBuilder.aggregation（aggregation);
searchRequest.source（searchSourceBuilder);
//执行查询操作
SearchResponse searchResponse = client.search（searchRequest, RequestOptions.DEFAULT);
//获取分组信息
Terms terms = searchResponse.getAggregations().get("age_term");
List<? extends Terms.Bucket> buckets = terms.getBuckets();
for (Terms.Bucket bucket: buckets) {
System.out.println（bucket.getKey()+"---"+bucket.getDocCount());
}
//关闭连接
client.close();
（3）程序运行后输出结果如下：
2，sum 聚合（统计每个学员的总成绩）
（1）假设我们需要统计统计每个学员的总成绩，首先调用 Elasticsearch 的 API 接口添加一些初始数据：
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/score/_doc/1' -d'{"name":"tom","subject":"chinese","score":59}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/score/_doc/2' -d'{"name":"tom","subject":"math","score":89}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/score/_doc/3' -d'{"name":"jack","subject":"chinese","score":78}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/score/_doc/4' -d'{"name":"jack","subject":"math","score":85}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/score/_doc/5' -d'{"name":"jessica","subject":"chinese","score":97}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/score/_doc/6' -d'{"name":"jessica","subject":"math","score":68}'
（2）下面是聚合统计样例代码，统计每个学员的总成绩：
//获取 RestClient 连接
RestHighLevelClient client = new RestHighLevelClient(
RestClient.builder(
new HttpHost("192.168.121.128", 9200, "http"),
new HttpHost("192.168.121.129", 9200, "http"),
new HttpHost("192.168.121.130", 9200, "http")));
SearchRequest searchRequest = new SearchRequest();
searchRequest.indices("score");
//指定查询条件
SearchSourceBuilder searchSourceBuilder = new SearchSourceBuilder();
//指定分组和求 sum
TermsAggregationBuilder aggregation = AggregationBuilders.terms("name_term")
.field("name.keyword")//指定分组字段，如果是字符串（Text）类型，则需要指定使用 keyword 类型
//指定求 sum，也支持 avg、min、max 等操作
.subAggregation（AggregationBuilders.sum("sum_score").field("score"));
searchSourceBuilder.aggregation（aggregation);
searchRequest.source（searchSourceBuilder);
//执行查询操作
SearchResponse searchResponse = client.search（searchRequest, RequestOptions.DEFAULT);
//获取分组信息
Terms terms = searchResponse.getAggregations().get("name_term");
List<? extends Terms.Bucket> buckets = terms.getBuckets();
for (Terms.Bucket bucket: buckets) {
//获取 sum 聚合的结果
Sum sum = bucket.getAggregations().get("sum_score");
System.out.println（bucket.getKey()+"---"+sum.getValue());
}
//关闭连接
client.close();
（3）程序运行后输出结果如下：
附：aggregations 获取所有分组数据
1，默认只返回 10 个分组
（1）默认情况下，ES 只会返回 10 个分组的数据。我们在上面样例 1（统计相同年龄的学员个数）的基础上再初始化一批测试数据：
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/61' -d'{"name":"s1","age":31}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/62' -d'{"name":"s2","age":32}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/63' -d'{"name":"s3","age":33}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/64' -d'{"name":"s4","age":34}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/65' -d'{"name":"s5","age":35}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/66' -d'{"name":"s6","age":36}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/67' -d'{"name":"s7","age":37}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/68' -d'{"name":"s8","age":38}'
curl -H "Content-Type: application/json" -XPOST 'http://192.168.121.128:9200/stu/_doc/69' -d'{"name":"s9","age":39}'
（2）再次执行样例 1 代码，发现结果中返回的分组个数是 10 个，没有全部都显示出来。
（3）即使我们尝试增加分页数，结果还是 10 条数据。说明分页参数对分组数据是无效的。
searchSourceBuilder.from(0).size(20);
2，获取指定分组个数数据
（1）我们可以在在聚合操作上使用 size 方法进行设置获取指定分组个数数据，比如下面代码最多可以获取到 20 个分组数据：
TermsAggregationBuilder aggregation = AggregationBuilders.terms("age_term")
.field("age")
.size(20);//获取指定分组个数的数据
- 运行结果如下，因为我们设置做多获取 20 个分组的数据，而结果一共只有 12 个分组，所以全都获取到了。
（2）如果前期不确定到底有多少个分组的数据，还想获取到所有分组的数据，此时可以在 size 中设置一个 Integer 的最大值，这样基本上就没什么问题了。
注意：如果最后的分组个数太多，会给 ES 造成比较大的压力，所以官方在这做了限制，让用户手工指定获取多少分组的数据。
TermsAggregationBuilder aggregation = AggregationBuilders.terms("age_term")
.field("age")
.size（Integer.MAX_VALUE);//获取指定分组个数的数据
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