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From "Etienne Chauchot (JIRA)" <>
Subject [jira] [Commented] (BEAM-1261) State API should allow state to be managed in different windows
Date Thu, 30 Mar 2017 09:20:41 GMT


Etienne Chauchot commented on BEAM-1261:

I have one possible use case of this. I'm sure [~kenn] you know the one I'am talking about
In nexmark query3 uses state to do an incremental join of the auctions and the people. Auctions
and person events can arrive out of order and in different (fixed) windows
- person element is stored in state in order to match future auctions by that person
- auction elements are stored in state until we have seen the corresponding person record
But state seem to become useless for this query because it is actually scoped to a window,
so when the stored element will be needed in a future window, it will not be there anymore.

> State API should allow state to be managed in different windows
> ---------------------------------------------------------------
>                 Key: BEAM-1261
>                 URL:
>             Project: Beam
>          Issue Type: New Feature
>          Components: beam-model, sdk-java-core
>            Reporter: Ben Chambers
> For example, even if the elements are being processed in fixed windows of an hour, it
may be desirable for the state to "roll over" between windows (or be available to all windows).
> It will also be necessary to figure out when this state should be deleted (TTL? maximum
> Another problem is how to deal with out of order data. If data comes in from the 10:00
AM window, should its state changes be visible to the data in the 9:00 AM window? 

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