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https://issues.apache.org/jira/browse/FLINK-3761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15298360#comment-15298360
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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-221311349
Jip, this last paragraph with the Factory is what I hinted at with my
comment. 😃 This may be somewhat academic but if there is a method
`getPartitionedStateBackend` the likelihood of it being wrongly used is
somewhat high.
> 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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