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https://issues.apache.org/jira/browse/FLINK-16039?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Manas Kale updated FLINK-16039:
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Summary: [Discuss] Add API method to get last element in session window
(was: [Discussion] Add API method to get last element in session window)
> [Discuss] Add API method to get last element in session window
> --------------------------------------------------------------
>
> Key: FLINK-16039
> URL: https://issues.apache.org/jira/browse/FLINK-16039
> Project: Flink
> Issue Type: Improvement
> Components: API / DataStream
> Affects Versions: 1.10.0
> Reporter: Manas Kale
> Priority: Minor
>
> Consider the events :
> [1, event], [2, event]
> where first element is event timestamp in seconds and second element is event
> code/name.
> Also consider that an Event time session window with inactivityGap = 2
> seconds is acting on above stream.
> When the first event arrives, a session window should be created that is
> [1,1].
> When the second event arrives, a new session window should be created that is
> [2,2]. Since this falls within firstWindowTimestamp+inactivityGap, it should
> be merged into session window [1,2] and [2,2] should be deleted.
> This is my understanding of how session windows are created. *Please correct
> me if wrong.*
> However, Flink does not follow such a definition of windows semantically. If
> I call the getEnd() method of the TimeWindow() class, I get back _timestamp
> + inactivityGap_.
> For the above example, after processing the first element, I would get 1 + 2
> = 3 seconds as the window "end".
> The actual window end should be the timestamp 1, which is the last event in
> the session window.
> A solution would be to change the "end" definition of all windows, but I
> suppose this would be breaking and would need some debate.
> Therefore, I propose an intermediate solution : add a new API method that
> keeps track of the last element added in the session window.
> If there is agreement on this, I would like to start drafting a change
> document and implement this.
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