elasticsearch/docs/reference/aggregations/metrics/top-metrics-aggregation.asciidoc
Craig Taverner 5f7ea792ac
Soft-deprecation of point/geo_point formats (#86835)
* Soft-deprecation of point/geo_point formats

Since GeoJSON and WKT are now common formats for all three types:
  geo_shape, geo_point and point
We decided to soft-deprecate the other point formats by ordering:
* GeoJSON (object with keys `type` and `coordinates`)
* WKT `POINT(x y)`
* Object with keys `lat` and `lon` (or `x` and `y` for point)
* Array [lon,lat]
* String `"lat,lon"` (or `"x,y"` in point)
* String with geohash (only in `geo_point`)

The geohash is last because it is only in one field type.
The string version is second last because it is the most controversial
being the only version to reverse the coordinate order from all other
formats (for geo_point only, since the coordinates are not reversed
in point).

In addition we replaced many examples in both documentation and tests
to prioritize WKT over the plain string format.

Many remaining examples of array format or object with keys still exist
and could be replaced by, for example, GeoJSON, if we feel the need.

* Incorrect quote position
2022-05-17 23:46:43 +02:00

418 lines
9.2 KiB
Text

[role="xpack"]
[[search-aggregations-metrics-top-metrics]]
=== Top metrics aggregation
++++
<titleabbrev>Top metrics</titleabbrev>
++++
The `top_metrics` aggregation selects metrics from the document with the largest or smallest "sort"
value. For example, this gets the value of the `m` 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, "m": 3.1415}
{"index": {}}
{"s": 2, "m": 1.0}
{"index": {}}
{"s": 3, "m": 2.71828}
POST /test/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
"metrics": {"field": "m"},
"sort": {"s": "desc"}
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [ {"sort": [3], "metrics": {"m": 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
<<sort-search-results, 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 so which document wins ties is not specified.
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": "POINT (-78.6382 35.7796)"}}`::
gets metrics from the documents with `location` *closest* to `35.7796, -78.6382`
`"sort": "_score"`:: gets metrics from the document with the highest score
==== `metrics`
`metrics` selects the fields of the "top" document to return. You can request
a single metric with something like `"metrics": {"field": "m"}` or multiple
metrics by requesting a list of metrics like `"metrics": [{"field": "m"}, {"field": "i"}`.
`metrics.field` supports the following field types:
* <<boolean,`boolean`>>
* <<ip,`ip`>>
* <<keyword,keywords>>
* <<number,numbers>>
Except for keywords, <<runtime,runtime fields>> for corresponding types are also
supported. `metrics.field` doesn't support fields with <<array,array values>>. A
`top_metric` aggregation on array values may return inconsistent results.
The following example runs a `top_metrics` aggregation on several field types.
[source,console,id=search-aggregations-metrics-top-metrics-list-of-metrics]
----
PUT /test
{
"mappings": {
"properties": {
"d": {"type": "date"}
}
}
}
POST /test/_bulk?refresh
{"index": {}}
{"s": 1, "m": 3.1415, "i": 1, "d": "2020-01-01T00:12:12Z", "t": "cat"}
{"index": {}}
{"s": 2, "m": 1.0, "i": 6, "d": "2020-01-02T00:12:12Z", "t": "dog"}
{"index": {}}
{"s": 3, "m": 2.71828, "i": -12, "d": "2019-12-31T00:12:12Z", "t": "chicken"}
POST /test/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
"metrics": [
{"field": "m"},
{"field": "i"},
{"field": "d"},
{"field": "t.keyword"}
],
"sort": {"s": "desc"}
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [ {
"sort": [3],
"metrics": {
"m": 2.718280076980591,
"i": -12,
"d": "2019-12-31T00:12:12.000Z",
"t.keyword": "chicken"
}
} ]
}
}
}
----
// TESTRESPONSE
==== `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, "m": 3.1415}
{"index": {}}
{"s": 2, "m": 1.0}
{"index": {}}
{"s": 3, "m": 2.71828}
POST /test/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
"metrics": {"field": "m"},
"sort": {"s": "desc"},
"size": 3
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [
{"sort": [3], "metrics": {"m": 2.718280076980591 } },
{"sort": [2], "metrics": {"m": 1.0 } },
{"sort": [1], "metrics": {"m": 3.1414999961853027 } }
]
}
}
}
----
// 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>>. If
you till want to raise it, use something like:
[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.
==== Examples
[[search-aggregations-metrics-top-metrics-example-terms]]
===== 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", "m": 1}
{"index": {}}
{"ip": "192.168.0.1", "date": "2020-01-01T02:01:01", "m": 2}
{"index": {}}
{"ip": "192.168.0.2", "date": "2020-01-01T02:01:01", "m": 3}
POST /node/_search?filter_path=aggregations
{
"aggs": {
"ip": {
"terms": {
"field": "ip"
},
"aggs": {
"tm": {
"top_metrics": {
"metrics": {"field": "m"},
"sort": {"date": "desc"}
}
}
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"ip": {
"buckets": [
{
"key": "192.168.0.1",
"doc_count": 2,
"tm": {
"top": [ {"sort": ["2020-01-01T02:01:01.000Z"], "metrics": {"m": 2 } } ]
}
},
{
"key": "192.168.0.2",
"doc_count": 1,
"tm": {
"top": [ {"sort": ["2020-01-01T02:01:01.000Z"], "metrics": {"m": 3 } } ]
}
}
],
"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.m": "desc"}
},
"aggs": {
"tm": {
"top_metrics": {
"metrics": {"field": "m"},
"sort": {"date": "desc"}
}
}
}
}
}
}
----
// TEST[continued]
Which returns:
[source,js]
----
{
"aggregations": {
"ip": {
"buckets": [
{
"key": "192.168.0.2",
"doc_count": 1,
"tm": {
"top": [ {"sort": ["2020-01-01T02:01:01.000Z"], "metrics": {"m": 3 } } ]
}
},
{
"key": "192.168.0.1",
"doc_count": 2,
"tm": {
"top": [ {"sort": ["2020-01-01T02:01:01.000Z"], "metrics": {"m": 2 } } ]
}
}
],
"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 surprising results: floating point fields are
always sorted independently of whole numbered fields.
[source,console,id=search-aggregations-metrics-top-metrics-mixed-sort]
----
POST /test/_bulk?refresh
{"index": {"_index": "test1"}}
{"s": 1, "m": 3.1415}
{"index": {"_index": "test1"}}
{"s": 2, "m": 1}
{"index": {"_index": "test2"}}
{"s": 3.1, "m": 2.71828}
POST /test*/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
"metrics": {"field": "m"},
"sort": {"s": "asc"}
}
}
}
}
----
Which returns:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [ {"sort": [3.0999999046325684], "metrics": {"m": 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 explicitly cast the whole number
fields to floating points with something like:
[source,console]
----
POST /test*/_search?filter_path=aggregations
{
"aggs": {
"tm": {
"top_metrics": {
"metrics": {"field": "m"},
"sort": {"s": {"order": "asc", "numeric_type": "double"}}
}
}
}
}
----
// TEST[continued]
Which returns the much more expected:
[source,js]
----
{
"aggregations": {
"tm": {
"top": [ {"sort": [1.0], "metrics": {"m": 3.1414999961853027 } } ]
}
}
}
----
// TESTRESPONSE