文章目录

• 1、背景
• 2、需求
• 3、前置准备
• • 3.1 准备mapping
  • 3.2 准备数据
• 4、实现需求
• • 4.1 dsl
  • 4.2 java代码
  • 4.3 运行结果
• 5、max_doc_count 和 search.max_buckets
• 6、注意事项
• 7、完整代码
• 8、参考文档

1、背景

我们知道当我们使用 terms聚合时，当修改默认顺序为_count asc时，统计的结果是不准备的，而且官方也不推荐我们这样做，而是推荐使用rare terms聚合。rare terms是一个稀少的term聚合，可以一定程度的解决升序问题。

2、需求

统计province字段中包含上和湖的term数据，并且最多只能出现2次。获取到聚合后的结果。

3、前置准备

3.1 准备mapping

PUT /index_person
{"settings": {"number_of_shards": 1},"mappings": {"properties": {"id": {"type": "long"},"name": {"type": "keyword"},"province": {"type": "keyword"},"sex": {"type": "keyword"},"age": {"type": "integer"},"pipeline_province_sex":{"type": "keyword"},"address": {"type": "text","analyzer": "ik_max_word","fields": {"keyword": {"type": "keyword","ignore_above": 256}}}}}
}

3.2 准备数据

PUT /_bulk
{"create":{"_index":"index_person","_id":1}}
{"id":1,"name":"张三","sex":"男","age":20,"province":"湖北","address":"湖北省黄冈市罗田县匡河镇"}
{"create":{"_index":"index_person","_id":2}}
{"id":2,"name":"李四","sex":"男","age":19,"province":"江苏","address":"江苏省南京市"}
{"create":{"_index":"index_person","_id":3}}
{"id":3,"name":"王武","sex":"女","age":25,"province":"湖北","address":"湖北省武汉市江汉区"}
{"create":{"_index":"index_person","_id":4}}
{"id":4,"name":"赵六","sex":"女","age":30,"province":"北京","address":"北京市东城区"}
{"create":{"_index":"index_person","_id":5}}
{"id":5,"name":"钱七","sex":"女","age":16,"province":"北京","address":"北京市西城区"}
{"create":{"_index":"index_person","_id":6}}
{"id":6,"name":"王八","sex":"女","age":45,"province":"北京","address":"北京市朝阳区"}
{"create":{"_index":"index_person","_id":7}}
{"id":7,"name":"九哥","sex":"男","age":25,"province":"上海市","address":"上海市嘉定区"}

4、实现需求

4.1 dsl

GET /index_person/_search
{"size": 0,"aggs": {"agg_province": {"rare_terms": {"field": "province","max_doc_count": 2,"precision": 0.01,"include": "(.*上.*|.*湖.*|.*江.*)","exclude": ["江苏"],"missing": "default省"}}}
}

4.2 java代码

@Test
@DisplayName("稀少的term聚合，类似按照 _count asc 排序的terms聚合，但是terms聚合中按照_count asc的结果是不准的，需要使用 rare terms 聚合")
public void agg01() throws IOException {SearchRequest searchRequest = new SearchRequest.Builder().size(0).index("index_person").aggregations("agg_province", agg ->agg.rareTerms(rare ->// 稀有词 的字段rare.field("province")// 该稀有词最多可以出现在几个文档中，最大值为100，如果要调整，需要修改search.max_buckets参数的值(尝试修改这个值，不生效)// 在该例子中，只要是出现的次数<=2的聚合都会返回.maxDocCount(2L)// 内部布谷鸟过滤器的精度，精度越小越准，但是相应的消耗内存也越多，最小值为 0.00001，默认值为 0.01.precision(0.01)// 应该包含在聚合的term, 当是单个字段是，可以写正则表达式.include(include -> include.regexp("(.*上.*|.*湖.*|.*江.*)"))// 排出在聚合中的term，当是集合时，需要写准确的值.exclude(exclude -> exclude.terms(Collections.singletonList("江苏")))// 当文档中缺失province字段时，给默认值.missing("default省"))).build();System.out.println(searchRequest);SearchResponse