Effective in version 10.2, you can use window functions in an Expression transformation to perform stateful calculations on the Spark engine. Window functions operate on a group of rows and calculate a single return value for every input row. You can use window functions to perform the following tasks:
Retrieve data from previous or subsequent rows.
Calculate a cumulative sum based on a group of rows.
Calculate a cumulative average based on a group of rows.
For more information, see the "Stateful Computing on the Spark Engine" chapter of the