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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-3761) Introduce key group state backend
Date Thu, 19 May 2016 10:45:13 GMT

    [ https://issues.apache.org/jira/browse/FLINK-3761?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15290885#comment-15290885
] 

ASF GitHub Bot commented on FLINK-3761:
---------------------------------------

Github user tillrohrmann commented on the pull request:

    https://github.com/apache/flink/pull/1988#issuecomment-220289629
  
    In order to support scaling for non-partitioned state, the next step could be the introduction
of a kind of union state. The idea would be to aggregate the non-partitioned state of each
subtask and then sending it to all subtasks upon recovery. Then every subtask can pick from
the union state what it needs for its execution


> 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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