midApache Spark
Explain Window Functions in Spark.
Updated May 5, 2026
Short answer
Window functions perform calculations across a group of rows related to the current row.
Deep explanation
They involve a WindowSpec which defines partitioning, ordering, and frame boundaries (e.g., row_number, rank, moving average).
Real-world example
Calculating a running total of sales for each store daily.
Common mistakes
- Not defining an 'orderBy' in a window spec that requires it (like rank), leading to non-deterministic results.
Follow-up questions
- Does Windowing cause a shuffle?