1、需求

从颜色到品牌进行下钻分析，每种颜色的平均价格，以及找到每种颜色下的每个品牌的平均价格

2、需求分析

下钻的意思是，已经分了一个组了，比如说按照颜色分组了，然后还要继续对这个分组内的数据，再次分组，比如一个颜色内还可以分成多个不同的品牌的组，最后对每个最小粒度的分组执行聚合分析操作，这就叫做下钻分析。

ES下钻分析就要对bucket进行多层嵌套，多次分组。

3、实现方式

GET /tvs/sales/_search
{
  "size": 0,
  "aggs": {
    "group_by_color": {
      "terms": {
        "field": "color"
      },
      "aggs": {
        "color_avg_price": {
          "avg": {
            "field": "price"
          }
        },
        "group_by_brand" : {
          "terms": {
            "field": "brand"
          },
          "aggs": {
            "brand_avg_price": {
              "avg": {
                "field": "price"
              }
            }
          }
        }
      }
    }
  }
}

4、结果分析

{
  "took": 7,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "failed": 0
  },
  "hits": {
    "total": 8,
    "max_score": 0,
    "hits": []
  },
  "aggregations": {
    "group_by_color": {
      "doc_count_error_upper_bound": 0,
      "sum_other_doc_count": 0,
      "buckets": [
        {
          "key": "红色",
          "doc_count": 4,
          "color_avg_price": {
            "value": 3250
          },
          "group_by_brand": {
            "doc_count_error_upper_bound": 0,
            "sum_other_doc_count": 0,
            "buckets": [
              {
                "key": "长虹",
                "doc_count": 3,
                "brand_avg_price": {
                  "value": 1666.6666666666667
                }
              },
              {
                "key": "三星",
                "doc_count": 1,
                "brand_avg_price": {
                  "value": 8000
                }
              }
            ]
          }
        },
        {
          "key": "绿色",
          "doc_count": 2,
          "color_avg_price": {
            "value": 2100
          },
          "group_by_brand": {
            "doc_count_error_upper_bound": 0,
            "sum_other_doc_count": 0,
            "buckets": [
              {
                "key": "TCL",
                "doc_count": 1,
                "brand_avg_price": {
                  "value": 1200
                }
              },
              {
                "key": "小米",
                "doc_count": 1,
                "brand_avg_price": {
                  "value": 3000
                }
              }
            ]
          }
        },
        {
          "key": "蓝色",
          "doc_count": 2,
          "color_avg_price": {
            "value": 2000
          },
          "group_by_brand": {
            "doc_count_error_upper_bound": 0,
            "sum_other_doc_count": 0,
            "buckets": [
              {
                "key": "TCL",
                "doc_count": 1,
                "brand_avg_price": {
                  "value": 1500
                }
              },
              {
                "key": "小米",
                "doc_count": 1,
                "brand_avg_price": {
                  "value": 2500
                }
              }
            ]
          }
        }
      ]
    }
  }
}

key：颜色
doc_count：该颜色下一共有多少document
color_avg_price.value：该颜色下全部document的平均值

group_by_brand：在该颜色下进行品牌分组
group_by_brand.key：该颜色下的某个品牌名称
group_by_brand.doc_count：该颜色下的某个品牌的document数
group_by_brand.brand_avg_price.value：该颜色下的某个品牌的document总数的平均值

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