Does Daft support window functions (e.g cumulative sum)

We do not yet. What are you looking to do?

Cumulative sum a number of transactions over multiple windows (I assume I could do it via a udf but wanted to know if there was an optimised version that already exists)

Ah gotcha. There is no native way to do that at the moment, but we are definitely thinking about window function support down the line. @jay do you know how this could be accomplished via a UDF?