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Max Bucket Aggregation

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Max Bucket Aggregation

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This functionality is in technical preview and may be changed or removed in a future release. Elastic will work to fix any issues, but features in technical preview are not subject to the support SLA of official GA features.

A sibling pipeline aggregation which identifies the bucket(s) with the maximum value of a specified metric in a sibling aggregation and outputs both the value and the key(s) of the bucket(s). The specified metric must be numeric and the sibling aggregation must be a multi-bucket aggregation.

Syntax

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A max_bucket aggregation looks like this in isolation:

{
    "max_bucket": {
        "buckets_path": "the_sum"
    }
}

Table 3. max_bucket Parameters

Parameter Name	Description	Required
`buckets_path`	The path to the buckets we wish to find the maximum for (see `buckets_path` Syntax for more details)	Required
`gap_policy`	The policy to apply when gaps are found in the data (see Dealing with gaps in the data for more details)	Optional, defaults to `skip`
`format`	format to apply to the output value of this aggregation	Optional, defaults to `null`

The following snippet calculates the maximum of the total monthly sales:

{
    "aggs" : {
        "sales_per_month" : {
            "date_histogram" : {
                "field" : "date",
                "interval" : "month"
            },
            "aggs": {
                "sales": {
                    "sum": {
                        "field": "price"
                    }
                }
            }
        },
        "max_monthly_sales": {
            "max_bucket": {
                "buckets_path": "sales_per_month>sales" 
            }
        }
    }
}

buckets_path instructs this max_bucket aggregation that we want the maximum value of the sales aggregation in the sales_per_month date histogram.

And the following may be the response:

{
   "aggregations": {
      "sales_per_month": {
         "buckets": [
            {
               "key_as_string": "2015/01/01 00:00:00",
               "key": 1420070400000,
               "doc_count": 3,
               "sales": {
                  "value": 550
               }
            },
            {
               "key_as_string": "2015/02/01 00:00:00",
               "key": 1422748800000,
               "doc_count": 2,
               "sales": {
                  "value": 60
               }
            },
            {
               "key_as_string": "2015/03/01 00:00:00",
               "key": 1425168000000,
               "doc_count": 2,
               "sales": {
                  "value": 375
               }
            }
         ]
      },
      "max_monthly_sales": {
          "keys": ["2015/01/01 00:00:00"], 
          "value": 550
      }
   }
}

keys is an array of strings since the maximum value may be present in multiple buckets

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