[[search-aggregations-metrics-max-aggregation]]
=== Max Aggregation

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.

Computing the max price value across all documents

[source,js]
--------------------------------------------------
{
    "aggs" : {
        "max_price" : { "max" : { "field" : "price" } }
    }
}
--------------------------------------------------

Response:

[source,js]
--------------------------------------------------
{
    ...

    "aggregations": {
        "max_price": {
            "value": 35
        }
    }
}
--------------------------------------------------

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

Computing the max price value across all document, this time using a script:

[source,js]
--------------------------------------------------
{
    "aggs" : {
        "max_price" : { "max" : { "script" : "doc['price'].value" } }
    }
}
--------------------------------------------------

TIP: The `script` parameter expects an inline script. Use `script_id` for indexed scripts and `script_file` for scripts in the `config/scripts/` directory.

==== Value Script

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:

[source,js]
--------------------------------------------------
{
    "aggs" : {
        "max_price_in_euros" : {
            "max" : {
                "field" : "price",
                "script" : "_value * conversion_rate",
                "params" : {
                    "conversion_rate" : 1.2
                }
            }
        }
    }
}
--------------------------------------------------

