[[search-aggregations-pipeline-cumulative-sum-aggregation]]
=== Cumulative Sum Aggregation

coming[2.0.0-beta1]

experimental[]

A parent pipeline aggregation which calculates the cumulative sum of a specified metric in a parent histogram (or date_histogram) 
aggregation. The specified metric must be numeric and the enclosing histogram must have `min_doc_count` set to `0` (default
for `histogram` aggregations).

==== Syntax

A `cumulative_sum` aggregation looks like this in isolation:

[source,js]
--------------------------------------------------
{
    "cumulative_sum": {
        "buckets_path": "the_sum"
    }
}
--------------------------------------------------

.`cumulative_sum` Parameters
|===
|Parameter Name |Description |Required |Default Value
|`buckets_path` |The path to the buckets we wish to find the cumulative sum for (see <<buckets-path-syntax>> for more
 details) |Required |
 |`format` |format to apply to the output value of this aggregation |Optional, defaults to `null` |
|===

The following snippet calculates the cumulative sum of the total monthly `sales`:

[source,js]
--------------------------------------------------
{
    "aggs" : {
        "sales_per_month" : {
            "date_histogram" : {
                "field" : "date",
                "interval" : "month"
            },
            "aggs": {
                "sales": {
                    "sum": {
                        "field": "price"
                    }
                },
                "cumulative_sales": {
                    "cumulative_sum": {
                        "buckets_path": "sales" <1>
                    }
                }
            }
        }
    }
}
--------------------------------------------------

<1> `buckets_path` instructs this cumulative sum aggregation to use the output of the `sales` aggregation for the cumulative sum

And the following may be the response:

[source,js]
--------------------------------------------------
{
   "aggregations": {
      "sales_per_month": {
         "buckets": [
            {
               "key_as_string": "2015/01/01 00:00:00",
               "key": 1420070400000,
               "doc_count": 3,
               "sales": {
                  "value": 550
               },
               "cumulative_sales": {
                  "value": 550
               }
            },
            {
               "key_as_string": "2015/02/01 00:00:00",
               "key": 1422748800000,
               "doc_count": 2,
               "sales": {
                  "value": 60
               },
               "cumulative_sales": {
                  "value": 610 
               }
            },
            {
               "key_as_string": "2015/03/01 00:00:00",
               "key": 1425168000000,
               "doc_count": 2,
               "sales": {
                  "value": 375
               },
               "cumulative_sales": {
                  "value": 985
               }
            }
         ]
      }
   }
}
--------------------------------------------------