Max aggregation
editMax aggregation
editA 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.
The min
and max
aggregation operate on the double
representation of
the data. As a consequence, the result may be approximate when running on longs
whose absolute value is greater than 2^53
.
Computing the max price value across all documents
POST /sales/_search?size=0 { "aggs": { "max_price": { "max": { "field": "price" } } } }
Response:
{ ... "aggregations": { "max_price": { "value": 200.0 } } }
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.
Script
editThe max
aggregation can also calculate the maximum of a script. The example
below computes the maximum price:
POST /sales/_search { "aggs" : { "max_price" : { "max" : { "script" : { "source" : "doc.price.value" } } } } }
This will use the Painless scripting language and no script parameters. To use a stored script use the following syntax:
POST /sales/_search { "aggs" : { "max_price" : { "max" : { "script" : { "id": "my_script", "params": { "field": "price" } } } } } }
Value Script
editLet’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, let’s 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:
POST /sales/_search { "aggs" : { "max_price_in_euros" : { "max" : { "field" : "price", "script" : { "source" : "_value * params.conversion_rate", "params" : { "conversion_rate" : 1.2 } } } } } }
Missing value
editThe 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.