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

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[[search-aggregations-reducer-max-bucket-aggregation]]
=== Max Bucket Aggregation
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A sibling reducer 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.
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==== Syntax
A `max_bucket` aggregation looks like this in isolation:
[source,js]
--------------------------------------------------
{
"max_bucket": {
"buckets_path": "the_sum"
}
}
--------------------------------------------------
.`max_bucket` Parameters
|===
|Parameter Name |Description |Required |Default Value
|`buckets_path` |The path to the buckets we wish to find the maximum for (see <<bucket-path-syntax>> for more
details |Required |
|===
The following snippet calculates the maximum of the total monthly `sales`:
[source,js]
--------------------------------------------------
{
"aggs" : {
"sales_per_month" : {
"date_histogram" : {
"field" : "date",
"interval" : "month"
},
"aggs": {
"sales": {
"sum": {
"field": "price"
}
}
}
},
"max_monthly_sales": {
"max_bucket": {
"buckets_paths": "sales_per_month>sales" <1>
}
}
}
}
--------------------------------------------------
<1> `bucket_paths` instructs this max_bucket aggregation that we want the maximum value of the `sales` aggregation in the
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`sales_per_month` date histogram.
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,
"sales": {
"value": 550
}
},
{
"key_as_string": "2015/02/01 00:00:00",
"key": 1422748800000,
"doc_count": 2,
"sales": {
"value": 60
}
},
{
"key_as_string": "2015/03/01 00:00:00",
"key": 1425168000000,
"doc_count": 2,
"sales": {
"value": 375
}
}
]
},
"max_monthly_sales": {
"keys": ["2015/01/01 00:00:00"], <1>
"value": 550
}
}
}
--------------------------------------------------
<1> `keys` is an array of strings since the maximum value may be present in multiple buckets