OpenSearch/docs/reference/aggregations/pipeline/bucket-selector-aggregation...

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[[search-aggregations-pipeline-bucket-selector-aggregation]]
=== 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.
NOTE: 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:
[source,js]
--------------------------------------------------
{
"bucket_selector": {
"buckets_path": {
"my_var1": "the_sum", <1>
"my_var2": "the_value_count"
},
"script": "params.my_var1 > params.my_var2"
}
}
--------------------------------------------------
// NOTCONSOLE
<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-params]]
.`bucket_selector` Parameters
[options="header"]
|===
|Parameter Name |Description |Required |Default Value
|`script` |The script to run for this aggregation. The script can be inline, file or indexed. (see <<modules-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 <<gap-policy>> for more
details)|Optional |`skip`
|===
The following snippet only retains buckets where the total sales for the month is more than 200:
[source,console]
--------------------------------------------------
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"
}
}
}
}
}
}
--------------------------------------------------
// TEST[setup:sales]
And the following may be the response:
[source,console-result]
--------------------------------------------------
{
"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
}
},<1>
{
"key_as_string": "2015/03/01 00:00:00",
"key": 1425168000000,
"doc_count": 2,
"total_sales": {
"value": 375.0
},
}
]
}
}
}
--------------------------------------------------
// TESTRESPONSE[s/"took": 11/"took": $body.took/]
// TESTRESPONSE[s/"_shards": \.\.\./"_shards": $body._shards/]
// TESTRESPONSE[s/"hits": \.\.\./"hits": $body.hits/]
<1> Bucket for `2015/02/01 00:00:00` has been removed as its total sales was less than 200