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https://issues.apache.org/jira/browse/FLINK-2550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14704756#comment-14704756
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Aljoscha Krettek commented on FLINK-2550:
-----------------------------------------
One possibility I see is that the result DataStream of a window operation is of
type {{DataStream<WindowResult<T, W>>}} (where {{W}} is a type that depends on
the window being used) instead of {{DataStream<T>}}. This would allow
downstream operations to retrieve the meta-information for the window:
{code:java}
DataStream input = ...
DataStram result = input
.keyBy(...)
.window(10 Sec).every(2 sec)
.sum(...)
.map( (WindowResult<TupleX, TimeWindow> r) -> "got aggregate r.result in time
window r.window" )
{code}
Another option would be to extends {{StreamRecord}} to also hold information
about the window. This would, however, mean that we introduce overhead in every
element sent, not just window result elements.
> Rework DataStream API
> ---------------------
>
> Key: FLINK-2550
> URL: https://issues.apache.org/jira/browse/FLINK-2550
> Project: Flink
> Issue Type: Improvement
> Components: Streaming
> Affects Versions: 0.9
> Reporter: Aljoscha Krettek
> Assignee: Aljoscha Krettek
> Fix For: 0.10
>
>
> After discussions on the mailing list we arrived at a consensus to rework the
> streaming API to make it more fool-proof and easier to use. The resulting
> design document is available here:
> https://cwiki.apache.org/confluence/display/FLINK/Streams+and+Operations+on+Streams
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