[GitHub] [kafka] showuon commented on pull request #11124: [WIP] KAFKA-12839: use sessionWindow to represent SlidingWindows

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showuon commented on pull request #11124:
URL: https://github.com/apache/kafka/pull/11124#issuecomment-887989639


   @mjsax @ableegoldman , I found we already had a `SessionWindow` to represent the close time interval: `[start,end]`. So I directly use it for `SlidingWindows` aggregation window creation. I think this is what we want, right?
   
   I have another thought, which is to rename the time interval related windows. Currently, we have 3 types of time interval window:
   `TimeWindow` -> to have `[start,end)` time interval
   `SessionWindow` -> to have `[start,end]` time interval
   `UnlimitedWindow` -> to have `[start, MAX_VALUE)` time interval
   
   I think the name `SessionWindow` is definitely not good here, especially we want to use it in `SlidingWindows` now, although it is only used for `SessionWindows` before. We should name them with time interval meaning, not the streaming window functions meaning. ex:
   `TimeWindow` ->  `LeftClosedRightOpenWindow`
   `SessionWindow` -> `ClosedTimeWindow`
   `UnlimitedWindow` -> `LeftClosedWindow`
   ref: the `Classification of intervals` section in https://en.wikipeadia.org/wiki/Interval_(mathematics)
   
   Because these 3 window types are internal use only, it is safe to rename them. What do you think?


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