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84a59f8447
Also adds a few small notes to the documentation regarding potentially unintuitive behavior
86 lines
2.8 KiB
Text
86 lines
2.8 KiB
Text
[[search-aggregations-metrics-valuecount-aggregation]]
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=== Value Count Aggregation
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A `single-value` metrics aggregation that counts the number of values that are extracted from the aggregated documents.
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These values can be extracted either from specific fields in the documents, or be generated by a provided script. Typically,
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this aggregator will be used in conjunction with other single-value aggregations. For example, when computing the `avg`
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one might be interested in the number of values the average is computed over.
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`value_count` does not de-duplicate values, so even if a field has duplicates (or a script generates multiple
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identical values for a single document), each value will be counted individually.
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[source,console]
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--------------------------------------------------
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POST /sales/_search?size=0
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{
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"aggs" : {
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"types_count" : { "value_count" : { "field" : "type" } }
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}
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}
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--------------------------------------------------
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// TEST[setup:sales]
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Response:
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[source,console-result]
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--------------------------------------------------
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{
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...
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"aggregations": {
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"types_count": {
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"value": 7
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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 (`types_count` above) also serves as the key by which the aggregation result can be
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retrieved from the returned response.
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==== Script
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Counting the values generated by a script:
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[source,console]
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--------------------------------------------------
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POST /sales/_search?size=0
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{
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"aggs" : {
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"type_count" : {
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"value_count" : {
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"script" : {
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"source" : "doc['type'].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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// TEST[setup:sales]
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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,console]
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--------------------------------------------------
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POST /sales/_search?size=0
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{
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"aggs" : {
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"types_count" : {
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"value_count" : {
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"script" : {
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"id": "my_script",
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"params" : {
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"field" : "type"
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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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// TEST[setup:sales,stored_example_script]
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NOTE:: Because `value_count` is designed to work with any field it internally treats all values as simple bytes.
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Due to this implementation, if `_value` script variable is used to fetch a value instead of accessing the field
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directly (e.g. a "value script"), the field value will be returned as a string instead of it's native format.
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