OpenSearch/docs/reference/aggregations/pipeline/max-bucket-aggregation.asci...

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[[search-aggregations-pipeline-max-bucket-aggregation]]
=== Max Bucket Aggregation
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
A `max_bucket` aggregation looks like this in isolation:
[source,js]
--------------------------------------------------
{
"max_bucket": {
"buckets_path": "the_sum"
}
}
--------------------------------------------------
// NOTCONSOLE
.`max_bucket` Parameters
|===
|Parameter Name |Description |Required |Default Value
|`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 <<gap-policy>> for more
details)|Optional | `skip`
|`format` |format to apply to the output value of this aggregation |Optional |`null`
|===
The following snippet calculates the maximum of the total monthly `sales`:
[source,js]
--------------------------------------------------
POST /sales/_search
{
"size": 0,
"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" <1>
}
}
}
}
--------------------------------------------------
// CONSOLE
// TEST[setup:sales]
<1> `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:
[source,js]
--------------------------------------------------
{
"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
}
}
]
},
"max_monthly_sales": {
"keys": ["2015/01/01 00:00:00"], <1>
"value": 550.0
}
}
}
--------------------------------------------------
// TESTRESPONSE[s/"took": 11/"took": $body.took/]
// TESTRESPONSE[s/"_shards": \.\.\./"_shards": $body._shards/]
// TESTRESPONSE[s/"hits": \.\.\./"hits": $body.hits/]
<1> `keys` is an array of strings since the maximum value may be present in multiple buckets