# Apply over window

> Supported in: Streaming

Applies the specified operation to batches of rows collected by the window. The operation receives the windowed rows and produces output rows.

**Transform categories**: Other

## Declared arguments

* **Dataset:** Input dataset to window and process.<br>*Table*
* **Operation:** The operation to apply to each windowed batch of rows.<br>*Lambda*
* **Window:** Window defining how rows should be collected into batches.<br>*Window*
* *optional* **Key by columns:** Columns on which to partition the input by key. The operation will be applied separately for each distinct key value.<br>*Set\<Column\<Binary | Boolean | Byte | Double | Float | Integer | Long | Short | String | Timestamp>>*