|NO.Z.00032|——————————|BigDataEnd|——|Hadoop&ElasticSearch.V32|——|ELK.v32|集群|QueryDSL|聚合分析.V3|

一、桶聚合

### --- Bucket Aggregations，桶聚合。

~~~     它执行的是对文档分组的操作（与sql中的group by类似），
~~~     把满足相关特性的文档分到一个桶里，即桶分，
~~~     输出结果往往是一个个包含多个文档的桶（一个桶就是一个group）
~~~     bucket：一个数据分组
~~~     metric：对一个数据分组执行的统计

### --- 桶聚合

POST /book/_search
{
"size": 0,
"aggs": {
"group_by_price": {
"range": {
"field": "price",
"ranges": [
{
"from": 0,
"to": 200
},
{
"from": 200,
"to": 400
},
{
"from": 400,
"to": 1000
}
]
},
"aggs": {
"average_price": {
"avg": {
"field": "price"
}
}
}
}
}
}

### --- 值的个数统计

"count_price": {
"value_count": {
"field": "price"
}
}

### --- 实现having 效果

POST /book/_search
{
  "size": 0,
  "aggs": {
  "group_by_price": {
  "range": {
  "field": "price",
  "ranges": [
  {
  "from": 0,
  "to": 200
  },
  {
  "from": 200,
  "to": 400
  },
  {
  "from": 400,
  "to": 1000
  }
  ]
  },
  "aggs": {
  "average_price": {
  "avg": {
  "field": "price"
  }
  },
  "having": {
  "bucket_selector": {
  "buckets_path": {
  "avg_price": "average_price"
  },
  "script": {
  "source": "params.avg_price >= 200 "
  }
  }
  }
  }
  }
}

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Walter Savage Landor:strove with none,for none was worth my strife.Nature I loved and, next to Nature, Art:I warm'd both hands before the fire of life.It sinks, and I am ready to depart

                                                                                                                                                   ——W.S.Landor

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