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https://issues.apache.org/jira/browse/FLINK-9428?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16488847#comment-16488847
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ASF GitHub Bot commented on FLINK-9428:
---------------------------------------

Github user StephanEwen commented on the issue:

    https://github.com/apache/flink/pull/6066
  
    Thanks for the review.
    
    Addressing the comments and merging this...


> Allow operators to flush data on checkpoint pre-barrier
> -------------------------------------------------------
>
>                 Key: FLINK-9428
>                 URL: https://issues.apache.org/jira/browse/FLINK-9428
>             Project: Flink
>          Issue Type: New Feature
>          Components: State Backends, Checkpointing
>            Reporter: Stephan Ewen
>            Assignee: Stephan Ewen
>            Priority: Major
>             Fix For: 1.6.0
>
>
> Some operators maintain some small transient state that may be inefficient to 
> checkpoint, especially when it would need to be checkpointed also in a 
> re-scalable way.
> An example are opportunistic pre-aggregation operators, which have small the 
> pre-aggregation state that is frequently flushed downstream.
> Rather that persisting that state in a checkpoint, it can make sense to flush 
> the data downstream upon a checkpoint, to let it be part of the downstream 
> operator's state.
> This feature is sensitive, because flushing state has a clean implication on 
> the downstream operator's checkpoint alignment. However, used with care, and 
> with the new back-pressure-based checkpoint alignment, this feature can be 
> very useful.
> Because it is sensitive, I suggest to make this only an internal feature 
> (accessible to operators) and NOT expose it in the public API at this point.



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