elasticsearch的嵌套聚合，下钻分析，聚合分析

将文本field的fielddata属性设置为true,才能聚合

PUT /ecommerce/_mapping/product
 {       
  "properties": {
   "tags": {  
             "type": "text",
            "fielddata": true
         }       
    }         
 }

聚合分析,算每个tag下的商品数量

GET /ecommerce/product/_search
{
  "size": 0, 
  "aggs":{
    "group_by_tags":{
      "terms": {
        "field": "tags"

      }
    }
  }
}

对名称中包含yagao的商品，计算每个tag下的商品数量

GET /ecommerce/product/_search
{
  "size": 0, 
  "query": {
    "match": {
      "name": "yagao"
    }

  }, 
  "aggs":{
    "group_by_tags":{
      "terms": {
        "field": "tags"

      }
    }
  }
}

先分组，再算每组的平均值，计算每个tag下的商品的平均价格

GET /ecommerce/product/_search
{
  "size": 0, 
  "aggs": {
    "group_by_tags": {
      "terms": {
        "field": "tags"
      },
      "aggs": {
        "arg_price": {
          "avg": {
            "field": "price"
          }
        }
      }
    }
  }
}

计算每个tag下的商品的平均价格，并且按照平均价格降序排序

GET /ecommerce/product/_search
{
  "size": 0, 
  "aggs": {
    "group_by_tags": {
      "terms": {
        "field": "tags",
        "order": {
          "arg_price": "desc"
        }
      },
      "aggs": {
        "arg_price": {
          "avg": {
            "field": "price"
          }
        }
      }
    }
  }
}

按照指定的价格范围区间进行分组，然后在每组内再按照tag进行分组，最后再计算每组的平均价格,下钻两次

GET /ecommerce/product/_search
{
  "size": 0,
  "aggs": {
    "group_by_price": {
      "range": {
        "field": "price",
        "ranges": [
          {
            "from": 0,
            "to": 20
          },
           {
            "from": 20,
            "to": 40
          },

           {
            "from": 40,
            "to": 60
          }
        ]
      },
      "aggs": {
        "group_by_tags": {
          "terms": {
            "field": "tags"
          },
          "aggs": {
            "avg_price": {
             "avg": {
               "field": "price"
             }
            }
          }
        }
      }
    }
  }

}