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Min bucket aggregation

A sibling pipeline aggregation which identifies the bucket(s) with the minimum 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

A min_bucket aggregation looks like this in isolation:

{
  "min_bucket": {
    "buckets_path": "the_sum"
  }
}

Table 58. min_bucket Parameters

Parameter Name	Description	Required	Default Value
`buckets_path`	The path to the buckets we wish to find the minimum 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	`skip`
`format`	format to apply to the output value of this aggregation	Optional	`null`

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

POST /sales/_search
{
  "size": 0,
  "aggs": {
    "sales_per_month": {
      "date_histogram": {
        "field": "date",
        "calendar_interval": "month"
      },
      "aggs": {
        "sales": {
          "sum": {
            "field": "price"
          }
        }
      }
    },
    "min_monthly_sales": {
      "min_bucket": {
        "buckets_path": "sales_per_month>sales" 
      }
    }
  }
}

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

And the following may be the response:

{
   "took": 11,
   "timed_out": false,
   "_shards": ...,
   "hits": ...,
   "aggregations": {
      "sales_per_month": {
         "buckets": [
            {
               "key_as_string": "2015/01/01 00:00:00",
               "key": 1420070400000,
               "doc_count": 3,
               "sales": {
                  "value": 550.0
               }
            },
            {
               "key_as_string": "2015/02/01 00:00:00",
               "key": 1422748800000,
               "doc_count": 2,
               "sales": {
                  "value": 60.0
               }
            },
            {
               "key_as_string": "2015/03/01 00:00:00",
               "key": 1425168000000,
               "doc_count": 2,
               "sales": {
                  "value": 375.0
               }
            }
         ]
      },
      "min_monthly_sales": {
          "keys": ["2015/02/01 00:00:00"], 
          "value": 60.0
      }
   }
}

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

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https://www.elastic.co/guide/en/elasticsearch/reference/7.17/search-aggregations-pipeline-min-bucket-aggregation.html