ES度量聚合(ElasticSearch Metric Aggregations)，Java开发自学教程

.value(

(new MultiValuesSourceFieldConfig.Builder())

.setFieldName(“num”)

.setMissing(0)

.build()

)

.weight(

(new MultiValuesSourceFieldConfig.Builder())

.setFieldName(“num”)

.setMissing(1)

.build()

)

// .valueType(ValueType.LONG)

;

avg.toString();

sourceBuilder.aggregation(avg);

sourceBuilder.size(0);

sourceBuilder.query(

QueryBuilders.termQuery(“sellerId”, 24)

);

searchRequest.source(sourceBuilder);

SearchResponse result = client.search(searchRequest, RequestOptions.DEFAULT);

System.out.println(result);

} catch (Throwable e) {

e.printStackTrace();

} finally {

EsClient.close(client);

}

}

Cardinality Aggregation

---

基数聚合，先distinct,再聚合，类似关系型数据库(count(distinct))。

示例如下：

POST /sales/_search?size=0

{

“aggs” : {

“type_count” : {

“cardinality” : {

“field” : “type”

}

}

}

}

对应的JAVA示例如下：

public static void test_Cardinality_Aggregation() {

RestHighLevelClient client = EsClient.getClient();

try {

SearchRequest searchRequest = new SearchRequest();

searchRequest.indices(“aggregations_index02”);

SearchSourceBuilder sourceBuilder = new SearchSourceBuilder();

AggregationBuilder aggregationBuild = AggregationBuilders.cardinality(“buyerid_count”).field(“buyerId”);

sourceBuilder.aggregation(aggregationBuild);

sourceBuilder.size(0);

sourceBuilder.query(

QueryBuilders.termQuery(“sellerId”, 24)

);

searchRequest.source(sourceBuilder);

SearchResponse result = client.search(searchRequest, RequestOptions.DEFAULT);

System.out.println(result);

} catch (Throwable e) {

e.printStackTrace();

} finally {

EsClient.close(client);

}

}

返回结果如下：

{

“took”:30,

“timed_out”:false,

“_shards”:{

“total”:5,

“successful”:5,

“skipped”:0,

“failed”:0

},

“hits”:{

“total”:39,

“max_score”:0,

“hits”:[

]

},

“aggregations”:{

“cardinality#type_count”:{

“value”:11

}

}

}

上述实现与SQL:SELECT COUNT(DISTINCT buyerId) from es_order_tmp where sellerId=24; 效果类似，表示购买了商家id为24的买家个数。

其核心参数如下：

• precision_threshold

精确度控制。在此计数之下，期望计数接近准确。在这个值之上，计数可能会变得更加模糊（不准确）。支持的最大值是40000，超过此值的阈值与40000的阈值具有相同的效果。默认值是3000。

上述示例中返回的11是精确值，如果改写成下面的代码，结果将变的不准确：

field(“buyerId