[[search-aggregations-pipeline-bucket-selector-aggregation]] === Bucket Selector Aggregation experimental[] 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. Note: The bucket_selector aggregation, like all pipeline aggregations, executions 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: [source,js] -------------------------------------------------- { "bucket_selector": { "buckets_path": { "my_var1": "the_sum", <1> "my_var2": "the_value_count" }, "script": "my_var1 > my_var2" } } -------------------------------------------------- <1> 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. .`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 <> 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 <> for more details) |Required | |`gap_policy` |The policy to apply when gaps are found in the data (see <> for more details)|Optional, defaults to `skip` | |=== The following snippet only retains buckets where the total sales for the month is less than or equal to 50: [source,js] -------------------------------------------------- { "aggs" : { "sales_per_month" : { "date_histogram" : { "field" : "date", "interval" : "month" }, "aggs": { "total_sales": { "sum": { "field": "price" } }, "sales_bucket_filter": { "bucket_selector": { "buckets_path": { "totalSales": "total_sales" }, "script": "totalSales <= 50" } } } } } } -------------------------------------------------- And the following may be the response: [source,js] -------------------------------------------------- { "aggregations": { "sales_per_month": { "buckets": [ { "key_as_string": "2015/01/01 00:00:00", "key": 1420070400000, "doc_count": 3, "total_sales": { "value": 50 } },<1> { "key_as_string": "2015/03/01 00:00:00", "key": 1425168000000, "doc_count": 2, "total_sales": { "value": 40 }, } ] } } } -------------------------------------------------- <1> Bucket for `2015/02/01 00:00:00` has been removed as its total sales exceeded 50