[role="xpack"]
[testenv="basic"]
[[preview-data-frame-transform]]
=== Preview {dataframe-transforms} API

[subs="attributes"]
++++
<titleabbrev>Preview {dataframe-transforms}</titleabbrev>
++++

Previews a {dataframe-transform}.


==== Request

`POST _data_frame/transforms/_preview`

//==== Description
//==== Path Parameters
//==== Authorization

==== Request Body

`source`:: The source index or index pattern.

`pivot`:: Defines the pivot function `group by` fields and the aggregation to
reduce the data.


==== Examples

The following example obtains a preview of a {dataframe-transform} on the {kib}
eCommerce sample data:

[source,js]
--------------------------------------------------
POST _data_frame/transforms/_preview
{
  "source": "kibana_sample_data_ecommerce",
  "pivot": {
    "group_by": {
      "customer_id": {
        "terms": {
          "field": "customer_id"
        }
      }
    },
    "aggregations": {
      "max_price": {
        "max": {
          "field": "taxful_total_price"
        }
      }
    }
  }
}
--------------------------------------------------
// CONSOLE
// TEST[skip:set up sample data]

The data that is returned for this example is as follows:
[source,js]
----
{
  "preview" : [
    {
      "max_price" : 171.0,
      "customer_id" : "10"
    },
    {
      "max_price" : 233.0,
      "customer_id" : "11"
    },
    {
      "max_price" : 200.0,
      "customer_id" : "12"
    }
    ...
  ]
}
----
// NOTCONSOLE
