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[role="xpack"]
[testenv="basic"]
[[search-aggregations-metrics-top-metrics]]
=== Top Metrics Aggregation
experimental[We expect to change the response format of this aggregation as we add more features., https://github.com/elastic/elasticsearch/issues/51813]
The `top_metrics` aggregation selects metrics from the document with the largest or smallest "sort"
value. For example, This gets the value of the `v` field on the document with the largest value of `s`:
[source,console,id=search-aggregations-metrics-top-metrics-simple]
----
POST /test/_bulk?refresh
{"index": {}}
{"s": 1, "v": 3.1415}
{"index": {}}
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{"s": 2, "v": 1.0}
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{"index": {}}
{"s": 3, "v": 2.71828}
POST /test/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
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"metrics": {"field": "v"},
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"sort": {"s": "desc"}
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [ {"sort": [3], "metrics": {"v": 2.718280076980591 } } ]
}
}
}
----
// TESTRESPONSE
`top_metrics` is fairly similar to <<search-aggregations-metrics-top-hits-aggregation, `top_hits`>>
in spirit but because it is more limited it is able to do its job using less memory and is often
faster.
==== `sort`
The `sort` field in the metric request functions exactly the same as the `sort` field in the
<<request-body-search-sort, search>> request except:
* It can't be used on <<binary,binary>>, <<flattened,flattened>, <<ip,ip>>,
<<keyword,keyword>>, or <<text,text>> fields.
* It only supports a single sort value.
The metrics that the aggregation returns is the first hit that would be returned by the search
request. So,
`"sort": {"s": "desc"}`:: gets metrics from the document with the highest `s`
`"sort": {"s": "asc"}`:: gets the metrics from the document with the lowest `s`
`"sort": {"_geo_distance": {"location": "35.7796, -78.6382"}}`::
gets metrics from the documents with `location` *closest* to `35.7796, -78.6382`
`"sort": "_score"`:: gets metrics from the document with the highest score
NOTE: This aggregation doesn't support any sort of "tie breaking". If two documents have
the same sort values then this aggregation could return either document's fields.
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==== `metrics`
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`metrics` selects the fields to of the "top" document to return.
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You can return multiple metrics by providing a list:
[source,console,id=search-aggregations-metrics-top-metrics-list-of-metrics]
----
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PUT /test
{
"mappings": {
"properties": {
"d": {"type": "date"}
}
}
}
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POST /test/_bulk?refresh
{"index": {}}
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{"s": 1, "v": 3.1415, "m": 1, "d": "2020-01-01T00:12:12Z"}
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{"index": {}}
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{"s": 2, "v": 1.0, "m": 6, "d": "2020-01-02T00:12:12Z"}
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{"index": {}}
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{"s": 3, "v": 2.71828, "m": -12, "d": "2019-12-31T00:12:12Z"}
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POST /test/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
"metrics": [
{"field": "v"},
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{"field": "m"},
{"field": "d"}
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],
"sort": {"s": "desc"}
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [ {
"sort": [3],
"metrics": {
"v": 2.718280076980591,
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"m": -12,
"d": "2019-12-31T00:12:12.000Z"
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}
} ]
}
}
}
----
// TESTRESPONSE
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==== `size`
`top_metrics` can return the top few document's worth of metrics using the size parameter:
[source,console,id=search-aggregations-metrics-top-metrics-size]
----
POST /test/_bulk?refresh
{"index": {}}
{"s": 1, "v": 3.1415}
{"index": {}}
{"s": 2, "v": 1.0}
{"index": {}}
{"s": 3, "v": 2.71828}
POST /test/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
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"metrics": {"field": "v"},
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"sort": {"s": "desc"},
"size": 2
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [
{"sort": [3], "metrics": {"v": 2.718280076980591 } },
{"sort": [2], "metrics": {"v": 1.0 } }
]
}
}
}
----
// TESTRESPONSE
The default `size` is 1. The maximum default size is `10` because the aggregation's
working storage is "dense", meaning we allocate `size` slots for every bucket. `10`
is a *very* conservative default maximum and you can raise it if you need to by
changing the `top_metrics_max_size` index setting. But know that large sizes can
take a fair bit of memory, especially if they are inside of an aggregation which
makes many buckes like a large
<<search-aggregations-metrics-top-metrics-example-terms, terms aggregation>>.
[source,console]
----
PUT /test/_settings
{
"top_metrics_max_size": 100
}
----
// TEST[continued]
NOTE: If `size` is more than `1` the `top_metrics` aggregation can't be the target of a sort.
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==== Examples
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[[search-aggregations-metrics-top-metrics-example-terms]]
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===== Use with terms
This aggregation should be quite useful inside of <<search-aggregations-bucket-terms-aggregation, `terms`>>
aggregation, to, say, find the last value reported by each server.
[source,console,id=search-aggregations-metrics-top-metrics-terms]
----
PUT /node
{
"mappings": {
"properties": {
"ip": {"type": "ip"},
"date": {"type": "date"}
}
}
}
POST /node/_bulk?refresh
{"index": {}}
{"ip": "192.168.0.1", "date": "2020-01-01T01:01:01", "v": 1}
{"index": {}}
{"ip": "192.168.0.1", "date": "2020-01-01T02:01:01", "v": 2}
{"index": {}}
{"ip": "192.168.0.2", "date": "2020-01-01T02:01:01", "v": 3}
POST /node/_search?filter_path=aggregations
{
"aggs": {
"ip": {
"terms": {
"field": "ip"
},
"aggs": {
"tm": {
"top_metrics": {
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"metrics": {"field": "v"},
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"sort": {"date": "desc"}
}
}
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"ip": {
"buckets": [
{
"key": "192.168.0.1",
"doc_count": 2,
"tm": {
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"top": [ {"sort": ["2020-01-01T02:01:01.000Z"], "metrics": {"v": 2 } } ]
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}
},
{
"key": "192.168.0.2",
"doc_count": 1,
"tm": {
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"top": [ {"sort": ["2020-01-01T02:01:01.000Z"], "metrics": {"v": 3 } } ]
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}
}
],
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0
}
}
}
----
// TESTRESPONSE
Unlike `top_hits`, you can sort buckets by the results of this metric:
[source,console]
----
POST /node/_search?filter_path=aggregations
{
"aggs": {
"ip": {
"terms": {
"field": "ip",
"order": {"tm.v": "desc"}
},
"aggs": {
"tm": {
"top_metrics": {
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"metrics": {"field": "v"},
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"sort": {"date": "desc"}
}
}
}
}
}
}
----
// TEST[continued]
Which returns:
[source,js]
----
{
"aggregations": {
"ip": {
"buckets": [
{
"key": "192.168.0.2",
"doc_count": 1,
"tm": {
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"top": [ {"sort": ["2020-01-01T02:01:01.000Z"], "metrics": {"v": 3 } } ]
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}
},
{
"key": "192.168.0.1",
"doc_count": 2,
"tm": {
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"top": [ {"sort": ["2020-01-01T02:01:01.000Z"], "metrics": {"v": 2 } } ]
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}
}
],
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0
}
}
}
----
// TESTRESPONSE
===== Mixed sort types
Sorting `top_metrics` by a field that has different types across different
indices producs somewhat suprising results: floating point fields are
always sorted independantly of whole numbered fields.
[source,console,id=search-aggregations-metrics-top-metrics-mixed-sort]
----
POST /test/_bulk?refresh
{"index": {"_index": "test1"}}
{"s": 1, "v": 3.1415}
{"index": {"_index": "test1"}}
{"s": 2, "v": 1}
{"index": {"_index": "test2"}}
{"s": 3.1, "v": 2.71828}
POST /test*/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
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"metrics": {"field": "v"},
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"sort": {"s": "asc"}
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [ {"sort": [3.0999999046325684], "metrics": {"v": 2.718280076980591 } } ]
}
}
}
----
// TESTRESPONSE
While this is better than an error it *probably* isn't what you were going for.
While it does lose some precision, you can explictly cast the whole number
fields to floating points with something like:
[source,console]
----
POST /test*/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
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"metrics": {"field": "v"},
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"sort": {"s": {"order": "asc", "numeric_type": "double"}}
}
}
}
}
----
// TEST[continued]
Which returns the much more expected:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [ {"sort": [1.0], "metrics": {"v": 3.1414999961853027 } } ]
}
}
}
----
// TESTRESPONSE
