Current state: Under Discussion
Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]
Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).
In KIP-450: Sliding Window Aggregations in the DSL, we introduce Sliding Window to do calculations for each distinct window, the sliding window implementation would be a more efficient way to do these types of aggregations. In the Sliding Window, we was planning to have windows with inclusive on both the start and end time, but currently, we implemented in TimeWindow which is a half-open time interval. We should introduce a new window type: SlidingWindow, to have "\[start, end]" time interval, for SlidingWindows aggregation.
This KIP will change the KStreamSlidingWindowAggregate implementation, to replace the original TimeWindow type, with the new SlidingWindow type. So that we can have correct aggregation calculation for the set of records within the window.
Ex: In KIP-450, we have a graph to describe what expected result we want:
But because of we used the TimeWindow to represent the window time interval, it actually has 1 ms difference for each window.
ex: originally, we expected have a window \[-7, 3], but we actually have a window \[-7, 2], or \[-7, 3)
After this KIP, this issue will be fixed and have a correct aggregation calculation results.
Compatibility, Deprecation, and Migration Plan
No migration plan is needed.