[role="xpack"]
[testenv="basic"]
[[search-aggregations-metrics-rate-aggregation]]
=== Rate aggregation
++++
<titleabbrev>Rate</titleabbrev>
++++

A `rate` metrics aggregation can be used only inside a `date_histogram` and calculates a rate of documents or a field in each
`date_histogram` bucket. The field values can be generated by a provided script or extracted from specific numeric or
<<histogram,histogram fields>> in the documents.

==== Syntax

A `rate` aggregation looks like this in isolation:

[source,js]
--------------------------------------------------
{
  "rate": {
    "unit": "month",
    "field": "requests"
  }
}
--------------------------------------------------
// NOTCONSOLE

The following request will group all sales records into monthly bucket and than convert the number of sales transaction in each bucket
into per annual sales rate.

[source,console]
--------------------------------------------------
GET sales/_search
{
  "size": 0,
  "aggs": {
    "by_date": {
      "date_histogram": {
        "field": "date",
        "calendar_interval": "month"  <1>
      },
      "aggs": {
        "my_rate": {
          "rate": {
            "unit": "year"  <2>
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TEST[setup:sales]
<1> Histogram is grouped by month.
<2> But the rate is converted into annual rate.

The response will return the annual rate of transaction in each bucket. Since there are 12 months per year, the annual rate will
be automatically calculated by multiplying monthly rate by 12.

[source,console-result]
--------------------------------------------------
{
  ...
  "aggregations" : {
    "by_date" : {
      "buckets" : [
        {
          "key_as_string" : "2015/01/01 00:00:00",
          "key" : 1420070400000,
          "doc_count" : 3,
          "my_rate" : {
            "value" : 36.0
          }
        },
        {
          "key_as_string" : "2015/02/01 00:00:00",
          "key" : 1422748800000,
          "doc_count" : 2,
          "my_rate" : {
            "value" : 24.0
          }
        },
        {
          "key_as_string" : "2015/03/01 00:00:00",
          "key" : 1425168000000,
          "doc_count" : 2,
          "my_rate" : {
            "value" : 24.0
          }
        }
      ]
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[s/\.\.\./"took": $body.took,"timed_out": false,"_shards": $body._shards,"hits": $body.hits,/]

Instead of counting the number of documents, it is also possible to calculate a sum of all values of the fields in the documents in each
bucket or the number of values in each bucket. The following request will group all sales records into monthly bucket and than calculate
the total monthly sales and convert them into average daily sales.

[source,console]
--------------------------------------------------
GET sales/_search
{
  "size": 0,
  "aggs": {
    "by_date": {
      "date_histogram": {
        "field": "date",
        "calendar_interval": "month"  <1>
      },
      "aggs": {
        "avg_price": {
          "rate": {
            "field": "price", <2>
            "unit": "day"  <3>
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TEST[setup:sales]
<1> Histogram is grouped by month.
<2> Calculate sum of all sale prices
<3> Convert to average daily sales

The response will contain the average daily sale prices for each month.

[source,console-result]
--------------------------------------------------
{
  ...
  "aggregations" : {
    "by_date" : {
      "buckets" : [
        {
          "key_as_string" : "2015/01/01 00:00:00",
          "key" : 1420070400000,
          "doc_count" : 3,
          "avg_price" : {
            "value" : 17.741935483870968
          }
        },
        {
          "key_as_string" : "2015/02/01 00:00:00",
          "key" : 1422748800000,
          "doc_count" : 2,
          "avg_price" : {
            "value" : 2.142857142857143
          }
        },
        {
          "key_as_string" : "2015/03/01 00:00:00",
          "key" : 1425168000000,
          "doc_count" : 2,
          "avg_price" : {
            "value" : 12.096774193548388
          }
        }
      ]
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[s/\.\.\./"took": $body.took,"timed_out": false,"_shards": $body._shards,"hits": $body.hits,/]

By adding the `mode` parameter with the value `value_count`, we can change the calculation from `sum` to the number of values of the field:

[source,console]
--------------------------------------------------
GET sales/_search
{
  "size": 0,
  "aggs": {
    "by_date": {
      "date_histogram": {
        "field": "date",
        "calendar_interval": "month"  <1>
      },
      "aggs": {
        "avg_number_of_sales_per_year": {
          "rate": {
            "field": "price", <2>
            "unit": "year",  <3>
            "mode": "value_count" <4>
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TEST[setup:sales]
<1> Histogram is grouped by month.
<2> Calculate number of of all sale prices
<3> Convert to annual counts
<4> Changing the mode to value count

The response will contain the average daily sale prices for each month.

[source,console-result]
--------------------------------------------------
{
  ...
  "aggregations" : {
    "by_date" : {
      "buckets" : [
        {
          "key_as_string" : "2015/01/01 00:00:00",
          "key" : 1420070400000,
          "doc_count" : 3,
          "avg_number_of_sales_per_year" : {
            "value" : 36.0
          }
        },
        {
          "key_as_string" : "2015/02/01 00:00:00",
          "key" : 1422748800000,
          "doc_count" : 2,
          "avg_number_of_sales_per_year" : {
            "value" : 24.0
          }
        },
        {
          "key_as_string" : "2015/03/01 00:00:00",
          "key" : 1425168000000,
          "doc_count" : 2,
          "avg_number_of_sales_per_year" : {
            "value" : 24.0
          }
        }
      ]
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[s/\.\.\./"took": $body.took,"timed_out": false,"_shards": $body._shards,"hits": $body.hits,/]

By default `sum` mode is used.

`"mode": "sum"`:: calculate the sum of all values field
`"mode": "value_count"`:: use the number of values in the field

The `mode` parameter can only be used with fields and scripts.

==== Relationship between bucket sizes and rate

The `rate` aggregation supports all rate that can be used <<calendar_intervals,calendar_intervals parameter>> of `date_histogram`
aggregation. The specified rate should compatible with the `date_histogram` aggregation interval, i.e. it should be possible to
convert the bucket size into the rate. By default the interval of the `date_histogram` is used.

`"rate": "second"`:: compatible with all intervals
`"rate": "minute"`:: compatible with all intervals
`"rate": "hour"`:: compatible with all intervals
`"rate": "day"`:: compatible with all intervals
`"rate": "week"`:: compatible with all intervals
`"rate": "month"`:: compatible with only with `month`, `quarter` and `year` calendar intervals
`"rate": "quarter"`:: compatible with only with `month`, `quarter` and `year` calendar intervals
`"rate": "year"`:: compatible with only with `month`, `quarter` and `year` calendar intervals

There is also an additional limitations if the date histogram is not a direct parent of the rate histogram. In this case both rate interval
and histogram interval have to be in the same group: [`second`, ` minute`, `hour`, `day`, `week`] or [`month`, `quarter`, `year`]. For
example, if the date histogram is `month` based, only rate intervals of `month`, `quarter` or `year` are supported. If the date histogram
is `day` based, only  `second`, ` minute`, `hour`, `day`, and `week` rate intervals are supported.

==== Script

The `rate` aggregation also supports scripting. For example, if we need to adjust out prices before calculating rates, we could use
a script to recalculate them on-the-fly:

[source,console]
--------------------------------------------------
GET sales/_search
{
  "size": 0,
  "aggs": {
    "by_date": {
      "date_histogram": {
        "field": "date",
        "calendar_interval": "month"
      },
      "aggs": {
        "avg_price": {
          "rate": {
            "script": {  <1>
              "lang": "painless",
              "source": "doc['price'].value * params.adjustment",
              "params": {
                "adjustment": 0.9  <2>
              }
            }
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TEST[setup:sales]

<1> The `field` parameter is replaced with a `script` parameter, which uses the
script to generate values which percentiles are calculated on.
<2> Scripting supports parameterized input just like any other script.

[source,console-result]
--------------------------------------------------
{
  ...
  "aggregations" : {
    "by_date" : {
      "buckets" : [
        {
          "key_as_string" : "2015/01/01 00:00:00",
          "key" : 1420070400000,
          "doc_count" : 3,
          "avg_price" : {
            "value" : 495.0
          }
        },
        {
          "key_as_string" : "2015/02/01 00:00:00",
          "key" : 1422748800000,
          "doc_count" : 2,
          "avg_price" : {
            "value" : 54.0
          }
        },
        {
          "key_as_string" : "2015/03/01 00:00:00",
          "key" : 1425168000000,
          "doc_count" : 2,
          "avg_price" : {
            "value" : 337.5
          }
        }
      ]
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[s/\.\.\./"took": $body.took,"timed_out": false,"_shards": $body._shards,"hits": $body.hits,/]
