How to write custom Cubert UDAFs?

[Swapnil S]

Hi,

I have a scenario in which i need to pick the first non null element for each grouping key of CUBE operator.

Where can i find reference steps to write a custom aggregation function for CUBE operator in CUBERT.

The reference for it at link http://linkedin.github.io/Cubert/userdefined/aggregations.html is empty.

Thanks,

Swapnil Salunkhe