elasticsearch bucket 之rare terms聚合

目录

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<Object> response = client.search(searchRequest, Object.class);
    System.out.println(response);
}

一些注意事项都在注释中。

4.3 运行结果

《elasticsearch bucket 之rare terms聚合》

5、max_doc_count 和 search.max_buckets

《elasticsearch bucket 之rare terms聚合》

6、注意事项

  1. rare terms统计返回的数据没有大小限制,而且受max_doc_count参数的限制,比如:如果复合 max_doc_count 的分组有60个,那么这60个分组会直接返回。
  2. max_doc_count的值最大为100,貌似不能修改。
  3. 如果一台节点聚合收集的结果过多,那么很容易超过 search.max_buckets的值,此时就需要修改这个值。
# 临时修改
PUT /_cluster/settings
{"transient": {"search.max_buckets": 65536}}

# 永久修改
PUT /_cluster/settings
{"persistent": {"search.max_buckets": 65536}}

7、完整代码

https://gitee.com/huan1993/spring-cloud-parent/blob/master/es/es8-api/src/main/java/com/huan/es8/aggregations/bucket/RareTermsAggs.java

8、参考文档

  1. https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-rare-terms-aggregation.html
    原文作者:huan1993
    原文地址: https://www.cnblogs.com/huan1993/p/16916801.html
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