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Bucket selector aggregation

A parent pipeline aggregation which executes a script which determines whether the current bucket will be retained in the parent multi-bucket aggregation. The specified metric must be numeric and the script must return a boolean value. If the script language is expression then a numeric return value is permitted. In this case 0.0 will be evaluated as false and all other values will evaluate to true.

The bucket_selector aggregation, like all pipeline aggregations, executes after all other sibling aggregations. This means that using the bucket_selector aggregation to filter the returned buckets in the response does not save on execution time running the aggregations.

Syntax

A bucket_selector aggregation looks like this in isolation:

{
  "bucket_selector": {
    "buckets_path": {
      "my_var1": "the_sum",                     
      "my_var2": "the_value_count"
    },
    "script": "params.my_var1 > params.my_var2"
  }
}

Here, my_var1 is the name of the variable for this buckets path to use in the script, the_sum is the path to the metrics to use for that variable.

Table 50. bucket_selector Parameters

Parameter Name	Description	Required	Default Value
`script`	The script to run for this aggregation. The script can be inline, file or indexed. (see Scripting for more details)	Required
`buckets_path`	A map of script variables and their associated path to the buckets we wish to use for the variable (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`

The following snippet only retains buckets where the total sales for the month is more than 200:

POST /sales/_search
{
  "size": 0,
  "aggs": {
    "sales_per_month": {
      "date_histogram": {
        "field": "date",
        "calendar_interval": "month"
      },
      "aggs": {
        "total_sales": {
          "sum": {
            "field": "price"
          }
        },
        "sales_bucket_filter": {
          "bucket_selector": {
            "buckets_path": {
              "totalSales": "total_sales"
            },
            "script": "params.totalSales > 200"
          }
        }
      }
    }
  }
}

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,
               "total_sales": {
                   "value": 550.0
               }
            },
            {
               "key_as_string": "2015/03/01 00:00:00",
               "key": 1425168000000,
               "doc_count": 2,
               "total_sales": {
                   "value": 375.0
               }
            }
         ]
      }
   }
}

Bucket for 2015/02/01 00:00:00 has been removed as its total sales was less than 200

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