Cannot use WindowedStream.fold with EventTimeSessionWindows

[Jack Huang]

Hi all,

I want to window a series of events using SessionWindow and use fold
function to incrementally aggregate the result.

events
    .keyBy(_.id)
    .window(EventTimeSessionWindows.withGap(Time.minutes(1)))
    .fold(new Session)(eventFolder)

​
However I get

java.lang.UnsupportedOperationException: Fold cannot be used with a
merging WindowAssigner.

​

Does anyone have a workaround?



Thanks,
Jack