版本说明：

elasticsearch：elasticsearch-7.12.1

kibana：kibana-7.12.1-windows-x86_64

原始数据：

_index	_type	_id	_score	address	age	bir	id	name
jason_doc_10	_doc	L2aqNoABfXKo_Zq7BPkO	1	中国深圳	69	1650184553376	daZhaoLiu	大赵六
jason_doc_10	_doc	MGaqNoABfXKo_Zq7mfma	1	中国上海市宝山区	20	1649862303342	user001	大张三
jason_doc_10	_doc	MWaqNoABfXKo_Zq7mfma	1	中国上海市浦东区	50	1649862303342	user00100	小张三
jason_doc_10	_doc	MmaqNoABfXKo_Zq7mfma	1	中国上海市黄埔	34	1649862303342	00user1	李四
jason_doc_10	_doc	M2aqNoABfXKo_Zq7mfma	1	上海普陀区	45	1649862303342	user0011	大李四
jason_doc_10	_doc	NGaqNoABfXKo_Zq7mfma	1	中国北京市朝阳区	62	1649862303342	user2201	小李四
jason_doc_10	_doc	NWaqNoABfXKo_Zq7mfma	1	中国北京市东城	42	1649862303342	78user01	王五
jason_doc_10	_doc	NmaqNoABfXKo_Zq7mfma	1	中国北京市西城区	12	1649862303342	22	大王五
jason_doc_10	_doc	N2aqNoABfXKo_Zq7mfma	1	北京市海淀区	18	1649862303342	user01	小王五
jason_doc_10	_doc	OGasNoABfXKo_Zq77Pkx	1		10		test_save_01	测试save用户
jason_doc_10	_doc	OWasNoABfXKo_Zq77Pmu	1		20		test_save_02	测试save用户_02
jason_doc_10	_doc	OmasNoABfXKo_Zq77Pmu	1		30		test_save_03	测试save用户_03
jason_doc_10	_doc	Q2aeO4ABfXKo_Zq7TvlP	1	广东省广州市天河区	55	1650267672018	daZhaoLiu	王海

 因为数据的原因，我这里只有年龄age字段有重复的，所以根据age去重。

DSL请求：

GET /jason_doc_10/_search
{
  "size": 0,
  "aggs": {
    "distic_age": {
      "cardinality": {
        "field": "age"
      }
    } 
  }
}

响应结果：

{
  "took" : 0,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 13,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "distic_age" : {
      "value" : 12
    }
  }
}

java中的实现：

首先pom依赖：

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-elasticsearch</artifactId>
            <version>2.6.6</version>
        </dependency>
<!--  注意：这里使用的ES版本是7.12.1，所以我本地安装的ES和kibana也是7.12.1 -->

 配置的客户端：HighLevelClient

@SpringBootConfiguration
public class RestHingLevelClient {

    @Bean
    public RestClientBuilder restClientBuilder() {
        return RestClient.builder(createHttpHost("127.0.0.1:9200"));
    }

    @Bean
    public RestHighLevelClient restHighLevelClient(@Autowired RestClientBuilder restClientBuilder) {
        return new RestHighLevelClient(restClientBuilder);
    }

    private HttpHost createHttpHost(String ipPort) {
        String[] split = ipPort.split(":");
        String ip = split[0];
        int port = Integer.parseInt(split[1]);
        return new HttpHost(ip, port, "http");
    }
}

测试类：

@SpringBootTest
public class TestQueryDocument {

    @Autowired
    @Qualifier(value = "restHighLevelClient")
    RestHighLevelClient client;

    @Test
    public void testDistinctByAge() throws IOException {
        // 创建查询请求
        SearchRequest request = new SearchRequest();
        request.indices("jason_doc_10");
        // 创建查询条件
        SearchSourceBuilder builder = new SearchSourceBuilder();
        // 根据年龄去重，并起别名为：distic_age
        builder.aggregation(AggregationBuilders.cardinality("distic_age").field("age"));
        request.source(builder);
        // 查询
        SearchResponse response = client.search(request, RequestOptions.DEFAULT);
        Aggregations aggregations = response.getAggregations();
        ParsedCardinality cardinality = (ParsedCardinality) aggregations.asList().get(0);
        long count = cardinality.getValue();
        System.out.println("去重后的总数：" + count);
    }