137 lines
3.6 KiB
Plaintext
137 lines
3.6 KiB
Plaintext
[[search-aggregations-metrics-stats-aggregation]]
|
|
=== Stats Aggregation
|
|
|
|
A `multi-value` metrics aggregation that computes stats over numeric values extracted from the aggregated documents. These values can be extracted either from specific numeric fields in the documents, or be generated by a provided script.
|
|
|
|
The stats that are returned consist of: `min`, `max`, `sum`, `count` and `avg`.
|
|
|
|
Assuming the data consists of documents representing exams grades (between 0 and 100) of students
|
|
|
|
[source,console]
|
|
--------------------------------------------------
|
|
POST /exams/_search?size=0
|
|
{
|
|
"aggs": {
|
|
"grades_stats": { "stats": { "field": "grade" } }
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
// TEST[setup:exams]
|
|
|
|
The above aggregation computes the grades statistics over all documents. The aggregation type is `stats` and the `field` setting defines the numeric field of the documents the stats will be computed on. The above will return the following:
|
|
|
|
|
|
[source,console-result]
|
|
--------------------------------------------------
|
|
{
|
|
...
|
|
|
|
"aggregations": {
|
|
"grades_stats": {
|
|
"count": 2,
|
|
"min": 50.0,
|
|
"max": 100.0,
|
|
"avg": 75.0,
|
|
"sum": 150.0
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
// TESTRESPONSE[s/\.\.\./"took": $body.took,"timed_out": false,"_shards": $body._shards,"hits": $body.hits,/]
|
|
|
|
The name of the aggregation (`grades_stats` above) also serves as the key by which the aggregation result can be retrieved from the returned response.
|
|
|
|
==== Script
|
|
|
|
Computing the grades stats based on a script:
|
|
|
|
[source,console]
|
|
--------------------------------------------------
|
|
POST /exams/_search?size=0
|
|
{
|
|
"aggs": {
|
|
"grades_stats": {
|
|
"stats": {
|
|
"script": {
|
|
"lang": "painless",
|
|
"source": "doc['grade'].value"
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
// TEST[setup:exams]
|
|
|
|
This will interpret the `script` parameter as an `inline` script with the `painless` script language and no script parameters. To use a stored script use the following syntax:
|
|
|
|
[source,console]
|
|
--------------------------------------------------
|
|
POST /exams/_search?size=0
|
|
{
|
|
"aggs": {
|
|
"grades_stats": {
|
|
"stats": {
|
|
"script": {
|
|
"id": "my_script",
|
|
"params": {
|
|
"field": "grade"
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
// TEST[setup:exams,stored_example_script]
|
|
|
|
===== Value Script
|
|
|
|
It turned out that the exam was way above the level of the students and a grade correction needs to be applied. We can use a value script to get the new stats:
|
|
|
|
[source,console]
|
|
--------------------------------------------------
|
|
POST /exams/_search?size=0
|
|
{
|
|
"aggs": {
|
|
"grades_stats": {
|
|
"stats": {
|
|
"field": "grade",
|
|
"script": {
|
|
"lang": "painless",
|
|
"source": "_value * params.correction",
|
|
"params": {
|
|
"correction": 1.2
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
// TEST[setup:exams]
|
|
|
|
==== Missing value
|
|
|
|
The `missing` parameter defines how documents that are missing a value should be treated.
|
|
By default they will be ignored but it is also possible to treat them as if they
|
|
had a value.
|
|
|
|
[source,console]
|
|
--------------------------------------------------
|
|
POST /exams/_search?size=0
|
|
{
|
|
"aggs": {
|
|
"grades_stats": {
|
|
"stats": {
|
|
"field": "grade",
|
|
"missing": 0 <1>
|
|
}
|
|
}
|
|
}
|
|
}
|
|
--------------------------------------------------
|
|
// TEST[setup:exams]
|
|
|
|
<1> Documents without a value in the `grade` field will fall into the same bucket as documents that have the value `0`.
|