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32e23b9100
Most aggregations (terms, histogram, stats, percentiles, geohash-grid) now support a new `missing` option which defines the value to consider when a field does not have a value. This can be handy if you eg. want a terms aggregation to handle the same way documents that have "N/A" or no value for a `tag` field. This works in a very similar way to the `missing` option on the `sort` element. One known issue is that this option sometimes cannot make the right decision in the unmapped case: it needs to replace all values with the `missing` value but might not know what kind of values source should be produced (numerics, strings, geo points?). For this reason, we might want to add an `unmapped_type` option in the future like we did for sorting. Related to #5324
91 lines
2.7 KiB
Plaintext
91 lines
2.7 KiB
Plaintext
[[search-aggregations-metrics-max-aggregation]]
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=== Max Aggregation
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A `single-value` metrics aggregation that keeps track and returns the maximum value among the 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.
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Computing the max price value across all documents
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[source,js]
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--------------------------------------------------
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{
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"aggs" : {
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"max_price" : { "max" : { "field" : "price" } }
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}
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}
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--------------------------------------------------
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Response:
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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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"max_price": {
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"value": 35
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}
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}
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}
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--------------------------------------------------
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As can be seen, the name of the aggregation (`max_price` 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 max price value across all document, this time using a script:
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[source,js]
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--------------------------------------------------
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{
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"aggs" : {
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"max_price" : { "max" : { "script" : "doc['price'].value" } }
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}
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}
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--------------------------------------------------
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TIP: The `script` parameter expects an inline script. Use `script_id` for indexed scripts and `script_file` for scripts in the `config/scripts/` directory.
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==== Value Script
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Let's say that the prices of the documents in our index are in USD, but we would like to compute the max in EURO (and for the sake of this example, lets say the conversion rate is 1.2). We can use a value script to apply the conversion rate to every value before it is aggregated:
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[source,js]
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--------------------------------------------------
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{
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"aggs" : {
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"max_price_in_euros" : {
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"max" : {
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"field" : "price",
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"script" : "_value * conversion_rate",
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"params" : {
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"conversion_rate" : 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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==== 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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{
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"aggs" : {
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"grade_max" : {
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"max" : {
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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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<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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