ElasticSearch5.X添加度量聚合（二）

以你之姓@ 2022-06-06 14:07 191阅读 0赞

## 添加度量指标[编辑][Link 1] ##

前面的例子（[http://blog.csdn.net/wwd0501/article/details/78501842][http_blog.csdn.net_wwd0501_article_details_78501842]，测试数据跟上篇一样）告诉我们每个桶里面的文档数量，这很有用。 但通常，我们的应用需要提供更复杂的文档度量。 例如，每种颜色汽车的平均价格是多少？

为了获取更多信息，我们需要告诉 Elasticsearch 使用哪个字段，计算何种度量。 这需要将度量 嵌套 在桶内， 度量会基于桶内的文档计算统计结果。

让我们继续为汽车的例子加入 `average` 平均度量：

GET /cars/transactions/_search
    {
       "size" : 0,
       "aggs": {
          "colors": {
             "terms": {
                "field": "color"
             },
             "aggs": { 
                "avg_price": { 
                   "avg": {
                      "field": "price" 
                   }
                }
             }
          }
       }
    }

拷贝为 CURL [在 SENSE 中查看][SENSE]

<table style="border-collapse:collapse; border-spacing:0px; background-color:transparent; line-height:26px; color:rgb(68,68,68); font-size:15px; margin-bottom:1em; border:none; width:750px"> 
 <tbody style="line-height:26px; vertical-align:top"> 
  <tr style="line-height:26px"> 
   <td align="left" style="padding:0.75em 0.2em 0px; line-height:26px; font-size:15px; vertical-align:top; border-top:none; border-right:none; border-left:none; border-bottom:1px solid rgb(229,234,228)"> <p style="margin-top:0px; margin-bottom:10px; font-size:16px"><a href="https://www.elastic.co/guide/cn/elasticsearch/guide/current/_adding_a_metric_to_the_mix.html#CO186-1" style="background-color:transparent; color:rgb(0,169,229); outline:none" rel="nofollow"><span style="color:rgb(68,68,68)"><img src="https://www.elastic.co/guide/cn/elasticsearch/guide/current/images/icons/callouts/1.png" alt="" style="border:0px; vertical-align:middle"></span></a></p> </td> 
   <td align="left" style="padding:0.75em 0px 0px 0.2em; line-height:26px; font-size:15px; vertical-align:top; border-top:none; border-right:none; border-left:none; border-bottom:1px solid rgb(229,234,228)"> <p style="margin-top:0px; margin-bottom:10px; font-size:16px">为度量新增&nbsp;<code style="font-family:Consolas,Menlo,&quot;DejaVu Sans Mono&quot;,&quot;Bitstream Vera Sans Mono&quot;,&quot;Lucida Console&quot;; font-size:0.9em; padding:0px 3px; color:rgb(85,85,85); background:rgb(248,248,248); display:inline; word-wrap:break-word; width:auto; overflow-x:auto; vertical-align:middle">aggs</code>&nbsp;层。</p> </td> 
  </tr> 
  <tr style="line-height:26px"> 
   <td align="left" style="padding:0.75em 0.2em 0px; line-height:26px; font-size:15px; vertical-align:top; border-top:none; border-right:none; border-left:none; border-bottom:1px solid rgb(229,234,228)"> <p style="margin-top:0px; margin-bottom:10px; font-size:16px"><a href="https://www.elastic.co/guide/cn/elasticsearch/guide/current/_adding_a_metric_to_the_mix.html#CO186-2" style="background-color:transparent; color:rgb(0,169,229); outline:none" rel="nofollow"><span style="color:rgb(68,68,68)"><img src="https://www.elastic.co/guide/cn/elasticsearch/guide/current/images/icons/callouts/2.png" alt="" style="border:0px; vertical-align:middle"></span></a></p> </td> 
   <td align="left" style="padding:0.75em 0px 0px 0.2em; line-height:26px; font-size:15px; vertical-align:top; border-top:none; border-right:none; border-left:none; border-bottom:1px solid rgb(229,234,228)"> <p style="margin-top:0px; margin-bottom:10px; font-size:16px">为度量指定名字：&nbsp;<code style="font-family:Consolas,Menlo,&quot;DejaVu Sans Mono&quot;,&quot;Bitstream Vera Sans Mono&quot;,&quot;Lucida Console&quot;; font-size:0.9em; padding:0px 3px; color:rgb(85,85,85); background:rgb(248,248,248); display:inline; word-wrap:break-word; width:auto; overflow-x:auto; vertical-align:middle">avg_price</code>&nbsp;。</p> </td> 
  </tr> 
  <tr style="line-height:26px"> 
   <td align="left" style="padding:0.75em 0.2em 0px; line-height:26px; font-size:15px; vertical-align:top; border:none"> <p style="margin-top:0px; margin-bottom:10px; font-size:16px"><a href="https://www.elastic.co/guide/cn/elasticsearch/guide/current/_adding_a_metric_to_the_mix.html#CO186-3" style="background-color:transparent; color:rgb(0,169,229); outline:none" rel="nofollow"><span style="color:rgb(68,68,68)"><img src="https://www.elastic.co/guide/cn/elasticsearch/guide/current/images/icons/callouts/3.png" alt="" style="border:0px; vertical-align:middle"></span></a></p> </td> 
   <td align="left" style="padding:0.75em 0px 0px 0.2em; line-height:26px; font-size:15px; vertical-align:top; border:none"> <p style="margin-top:0px; margin-bottom:10px; font-size:16px">最后，为&nbsp;<code style="font-family:Consolas,Menlo,&quot;DejaVu Sans Mono&quot;,&quot;Bitstream Vera Sans Mono&quot;,&quot;Lucida Console&quot;; font-size:0.9em; padding:0px 3px; color:rgb(85,85,85); background:rgb(248,248,248); display:inline; word-wrap:break-word; width:auto; overflow-x:auto; vertical-align:middle">price</code>&nbsp;字段定义&nbsp;<code style="font-family:Consolas,Menlo,&quot;DejaVu Sans Mono&quot;,&quot;Bitstream Vera Sans Mono&quot;,&quot;Lucida Console&quot;; font-size:0.9em; padding:0px 3px; color:rgb(85,85,85); background:rgb(248,248,248); display:inline; word-wrap:break-word; width:auto; overflow-x:auto; vertical-align:middle">avg</code>&nbsp;度量。</p> </td> 
  </tr> 
 </tbody> 
</table>

正如所见，我们用前面的例子加入了新的 `aggs` 层。这个新的聚合层让我们可以将 `avg` 度量嵌套置于 `terms` 桶内。实际上，这就为每个颜色生成了平均价格。

正如 `颜色` 的例子，我们需要给度量起一个名字（ `avg_price` ）这样可以稍后根据名字获取它的值。最后，我们指定度量本身（ `avg` ）以及我们想要计算平均值的字段（ `price` ）：

{
    ...
       "aggregations": {
          "colors": {
             "buckets": [
                {
                   "key": "red",
                   "doc_count": 4,
                   "avg_price": { 
                      "value": 32500
                   }
                },
                {
                   "key": "blue",
                   "doc_count": 2,
                   "avg_price": {
                      "value": 20000
                   }
                },
                {
                   "key": "green",
                   "doc_count": 2,
                   "avg_price": {
                      "value": 21000
                   }
                }
             ]
          }
       }
    ...
    }

尽管响应只发生很小改变，实际上我们获得的数据是增长了。之前，我们知道有四辆红色的车，现在，红色车的平均价格是 $32，500 美元。这个信息可以直接显示在报表或者图形中。

java代码实现：

/**
          * Description:桶聚合查询中添加度量指标
          * 例：计算每种颜色汽车的平均价格是多少
          * 
          * @author wangweidong
          * CreateTime: 2017年11月9日 下午3:47:54
         */
        @Test
        public void bucketsMetricsAggregation() {
        	String index = "cars";
        	String type = "transactions";
        	SearchRequestBuilder searchRequestBuilder = client.prepareSearch(index).setTypes(type);
        	
            TermsAggregationBuilder colorsField = AggregationBuilders.terms("popular_colors").field("color.keyword");
            AvgAggregationBuilder avgPriceField = AggregationBuilders.avg("avg_price").field("price");
            colorsField.subAggregation(avgPriceField);
            
            searchRequestBuilder.addAggregation(colorsField);
            searchRequestBuilder.setSize(0);
            SearchResponse searchResponse = searchRequestBuilder.execute().actionGet();
            
            System.out.println(searchResponse.toString());
            
            Terms genders = searchResponse.getAggregations().get("popular_colors");
    	    for (Terms.Bucket entry : genders.getBuckets()) {
    	    	Object key = entry.getKey();      // Term
    	        Long count = entry.getDocCount(); // Doc count
    	        
    	        Aggregations agg = entry.getAggregations();
    	        Avg avg = agg.get("avg_price");
    	        Double avgPrice = avg.getValue();
    	        
    	        System.out.println(key + "车有" + count + "辆，平均每台车价格：" + avgPrice);
    	    }
        }

文章参考： [https://www.elastic.co/guide/cn/elasticsearch/guide/current/\_adding\_a\_metric\_to\_the\_mix.html][https_www.elastic.co_guide_cn_elasticsearch_guide_current_adding_a_metric_to_the_mix.html]

[Link 1]: https://github.com/elasticsearch-cn/elasticsearch-definitive-guide/edit/cn/300_Aggregations/21_add_metric.asciidoc
[http_blog.csdn.net_wwd0501_article_details_78501842]: http://blog.csdn.net/wwd0501/article/details/78501842
[SENSE]: http://localhost:5601/app/sense/?load_from=https://www.elastic.co/guide/cn/elasticsearch/guide/current/snippets/300_Aggregations/20_basic_example.json
[https_www.elastic.co_guide_cn_elasticsearch_guide_current_adding_a_metric_to_the_mix.html]: https://www.elastic.co/guide/cn/elasticsearch/guide/current/_adding_a_metric_to_the_mix.html