es - elasticsearch - aggs - metrics - avg

世界上并没有完美的程序，但是我们并不因此而沮丧，因为写程序就是一个不断追求完美的过程。

问：avg有什么特点？
答：

问：avg如何使用？
答：

# 删除
DELETE /avg_test

# 映射
PUT /avg_test
{
  "mappings": {
    "properties": {
      "name": {"type": "keyword"},
      "filter_type": {"type": "keyword"},
      "num": {"type": "integer"}
    }
  }
}

# 索引
POST /avg_test/_bulk?routing=1&refresh
{"index": {"_id": 1}}
{"name": "hello", "filter_type": "t1", "num": 3}
{"index": {"_id": 2}}
{"name": "me", "filter_type": "t2", "num": 5}
{"index": {"_id": 3}}
{"name": "me", "filter_type": "t1", "num": 18}
{"index": {"_id": 4}}
{"name": "hello", "filter_type": "t1", "num": 20}
{"index": {"_id": 5}}
{"name": "good", "filter_type": "t1", "num": 28}
{"index": {"_id": 6}}
{"name": "me", "filter_type": "t2", "num": 50}
{"index": {"_id": 7}}
{"name": "good", "filter_type": "t1", "num": 58}
{"index": {"_id": 8}}
{"name": "hello", "filter_type": "t1", "num": 88}

# 搜索
GET /avg_test/_search?size=0
{
  "aggs": {
    "avg_aggs": {
      "avg": {
        "field": "num"
      }
    }
  }
}

# 结果
{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 8,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "avg_aggs" : {
      "value" : 33.75
    }
  }
}

# 搜索
GET /avg_test/_search?size=0
{
  "aggs": {
    "avg_aggs": {
      "avg": {
        "script": {
          "source": "doc.num.value"
        }
      }
    }
  }
}

# 结果
{
  "took" : 22,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 8,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "avg_aggs" : {
      "value" : 33.75
    }
  }
}

# 搜索
GET /avg_test/_search?size=0
{
  "aggs": {
    "avg_aggs": {
      "avg": {
        "field": "num", 
        "script": {
          "lang": "painless",
          "source": "_value * params.mul",
          "params": {
            "mul": 10
          }
        }
      }
    }
  }
}

# 结果
{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 8,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "avg_aggs" : {
      "value" : 337.5
    }
  }
}

DELETE /avg_histo_test

PUT /avg_histo_test
{
  "mappings": {
    "properties": {
      "my_histo": {"type": "histogram"}
    }
  }
}

POST /avg_histo_test/_doc/1
{
  "name": "no1",
  "my_histo": {
    "values": [1, 2, 3, 4],
    "counts": [1, 2, 3, 4]
  }
}

GET /avg_histo_test/_mapping

POST /avg_histo_test/_doc/2
{
  "name": "no2",
  "my_histo": {
    "values": [7, 8, 9, 10],
    "counts": [7, 8, 9, 10]
  }
}

# 搜索 - value * count / 总count 的平均值
GET /avg_histo_test/_search?size=0
{
  "aggs": {
    "avg_aggs": {
      "avg": {
        "field": "my_histo"
      }
    }
  }
}

# 结果
{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 2,
      "relation" : "eq"
    },
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "avg_aggs" : {
      "value" : 7.363636363636363
    }
  }
}