Hey all, I think we are missing a quite useful feature that could be implemented (with some slight modifications) on top of the current windowing api.
We currently provide 2 ways of aggregating (or reducing) over streams: doing a continuous aggregation and always output the aggregated value (which cannot be done properly in parallel) or doing aggregation in a window periodically. What we don't have at the moment is periodic aggregations on the whole stream. I would even go as far as to remove the continuous outputting reduce/aggregate it and replace it with this version as this in return can be done properly in parallel. My suggestion would be that a call: dataStream.reduce(..) dataStream.sum(..) would return a windowed data stream where the window is the whole record history, and the user would need to define a trigger to get the actual reduced values like: dataStream.reduce(...).every(Time.of(4,sec)) to get the actual reduced results. dataStream.sum(...).every(...) I think the current data stream reduce/aggregation is very confusing without being practical for any normal use-case. Also this would be a very api breaking change (but I would still make this change as it is much more intuitive than the current behaviour) so I would try to push it before the release if we can agree. Cheers, Gyula
