十五、Elasticsearch 教程： 聚合计算

聚合框架用于收集搜索查询选择的所有数据。该框架由许多构建块组成，有助于构建复杂的数据摘要

下面的JSON 对象使用聚合函数的一般请求正文格式

"aggregations" : {
   "<aggregation_name>" : {
      "<aggregation_type>" : {
         <aggregation_body>
      }
      [,"meta" : { [<meta_data_body>] } ]?
      [,"aggregations" : { [<sub_aggregation>]+ } ]?
   }

Elasticsearch 提供了大量的聚合函数，它们都有各自不同的目的

矩阵聚合 ( Metrics )

这些聚合函数可以根据聚合文档的字段值计算度量值，而且有时可以从脚本生成一些值

数字矩阵既可以是单值，也可以是平均聚合或多值统计等

平均数聚合 ( avg )

该聚合函数用于计算文档中出现的任何数字字段的平均值

例如

POST http://localhost:9200/user_admin/_search?pretty

请求正文

{
   "aggs":{
      "avg_money":{"avg":{"field":"money"}}
   }

返回响应结果

{
  "took" : 160,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : 3,
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "user_admin",
        "_type" : "user",
        "_id" : "2",
        "_score" : 1.0,
        "_source" : {
          "nickname" : "雅少",
          "description" : "虚怀若谷",
          "street" : "四川大学",
          "city" : "Chengdu",
          "state" : "Sichuan",
          "zip" : "610044",
          "location" : [
            104.094537,
            30.640174
          ],
          "money" : 68023,
          "tags" : [
            "Python",
            "HTML"
          ],
          "vitality" : "7.8"
        }
      },
      {
        "_index" : "user_admin",
        "_type" : "user",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "nickname" : "站长",
          "description" : "pottercoding.cn 程序员波特，程序员编程资料站 ，教程 ",
          "street" : "东四十条",
          "city" : "Beijing",
          "state" : "Beijing",
          "zip" : "100007",
          "location" : [
            116.432727,
            39.937732
          ],
          "money" : 5201814,
          "tags" : [
            "PHP",
            "Python"
          ],
          "vitality" : "9.0"
        }
      },
      {
        "_index" : "user_admin",
        "_type" : "user",
        "_id" : "3",
        "_score" : 1.0,
        "_source" : {
          "nickname" : "歌者",
          "description" : "程序设计也是设计，研发新菜也是研发",
          "street" : "五道口",
          "city" : "Beijing",
          "state" : "Beijing",
          "zip" : "100083",
          "location" : [
            116.346346,
            39.999333
          ],
          "money" : 71128,
          "tags" : [
            "Java",
            "Scala"
          ],
          "vitality" : "6.9"
        }
      }
    ]
  },
  "aggregations" : {
    "avg_money" : {
      "value" : 1780321.6666666667
    }
  }