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https://issues.apache.org/jira/browse/FLINK-3761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15290909#comment-15290909
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ASF GitHub Bot commented on FLINK-3761:
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Github user aljoscha commented on the pull request:
https://github.com/apache/flink/pull/1988#issuecomment-220293946
Yeah, we were also wondering wether it would make sense to allow the state
itself to be repartitioned, i.e. union and then split into the new parallelism.
In this way we wouldn't read all state in every operator.
> Introduce key group state backend
> ---------------------------------
>
> Key: FLINK-3761
> URL: https://issues.apache.org/jira/browse/FLINK-3761
> Project: Flink
> Issue Type: Sub-task
> Components: state backends
> Reporter: Till Rohrmann
> Assignee: Till Rohrmann
>
> After an off-line discussion with [~aljoscha], we came to the conclusion that
> it would be beneficial to reflect the differences between a keyed and a
> non-keyed stream also in the state backends. A state backend which is used
> for a keyed stream offers a value, list, folding and value state and has to
> group its keys into key groups.
> A state backend for non-keyed streams can only offer a union state to make it
> work with dynamic scaling. A union state is a state which is broadcasted to
> all tasks in case of a recovery. The state backends can then select what
> information they need to recover from the whole state (formerly distributed).
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