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a03b6c2fa5
This commit adds back "id" as the key within a script to specify a stored script (which with file scripts now gone is no longer ambiguous). It also adds "source" as a replacement for "code". This is in an attempt to normalize how scripts are specified across both put stored scripts and script usages, including search template requests. This also deprecates the old inline/stored keys.
134 lines
3.8 KiB
Plaintext
134 lines
3.8 KiB
Plaintext
[[search-aggregations-metrics-avg-aggregation]]
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=== Avg Aggregation
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A `single-value` metrics aggregation that computes the average of numeric values that are 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.
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Assuming the data consists of documents representing exams grades (between 0
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and 100) of students we can average their scores with:
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[source,js]
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--------------------------------------------------
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POST /exams/_search?size=0
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{
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"aggs" : {
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"avg_grade" : { "avg" : { "field" : "grade" } }
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[setup:exams]
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The above aggregation computes the average grade over all documents. The aggregation type is `avg` and the `field` setting defines the numeric field of the documents the average will be computed on. The above will return the following:
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[source,js]
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--------------------------------------------------
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{
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...
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"aggregations": {
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"avg_grade": {
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"value": 75.0
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}
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}
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}
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--------------------------------------------------
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// TESTRESPONSE[s/\.\.\./"took": $body.took,"timed_out": false,"_shards": $body._shards,"hits": $body.hits,/]
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The name of the aggregation (`avg_grade` above) also serves as the key by which the aggregation result can be retrieved from the returned response.
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==== Script
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Computing the average grade based on a script:
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[source,js]
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--------------------------------------------------
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POST /exams/_search?size=0
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{
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"aggs" : {
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"avg_grade" : {
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"avg" : {
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"script" : {
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"source" : "doc.grade.value"
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}
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}
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[setup:exams]
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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:
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[source,js]
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--------------------------------------------------
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POST /exams/_search?size=0
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{
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"aggs" : {
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"avg_grade" : {
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"avg" : {
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"script" : {
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"id": "my_script",
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"params": {
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"field": "grade"
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}
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}
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}
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[setup:exams,stored_example_script]
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===== Value Script
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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 value script to get the new average:
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[source,js]
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--------------------------------------------------
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POST /exams/_search?size=0
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{
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"aggs" : {
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"avg_corrected_grade" : {
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"avg" : {
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"field" : "grade",
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"script" : {
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"lang": "painless",
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"source": "_value * params.correction",
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"params" : {
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"correction" : 1.2
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}
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}
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}
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[setup:exams]
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==== Missing value
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The `missing` parameter defines how documents that are missing a value should be treated.
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By default they will be ignored but it is also possible to treat them as if they
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had a value.
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[source,js]
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--------------------------------------------------
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POST /exams/_search?size=0
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{
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"aggs" : {
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"grade_avg" : {
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"avg" : {
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"field" : "grade",
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"missing": 10 <1>
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}
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}
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}
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}
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--------------------------------------------------
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// CONSOLE
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// TEST[setup:exams]
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<1> Documents without a value in the `grade` field will fall into the same bucket as documents that have the value `10`.
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