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https://issues.apache.org/jira/browse/FLINK-6969?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16062870#comment-16062870
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ASF GitHub Bot commented on FLINK-6969:
---------------------------------------

GitHub user sunjincheng121 opened a pull request:

    https://github.com/apache/flink/pull/4183

    [FLINK-6969][table]Add support for deferred computation for group win…

    In this PR. I have add support for deferred computation for group window 
aggregates.
    
    - [x] General
      - The pull request references the related JIRA issue 
("[FLINK-6969][table]Add support for deferred computation for group window 
aggregates")
      - The pull request addresses only one issue
      - Each commit in the PR has a meaningful commit message (including the 
JIRA id)
    
    - [ ] Documentation
      - Documentation has been added for new functionality
      - Old documentation affected by the pull request has been updated
      - JavaDoc for public methods has been added
    
    - [x] Tests & Build
      - Functionality added by the pull request is covered by tests
      - `mvn clean verify` has been executed successfully locally or a Travis 
build has passed


You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/sunjincheng121/flink FLINK-6969-PR

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/flink/pull/4183.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #4183
    
----
commit 4030a7e899994a851404a996b5bd76f805f24c34
Author: sunjincheng121 <sunjincheng...@gmail.com>
Date:   2017-06-23T23:03:45Z

    [FLINK-6969][table]Add support for deferred computation for group window 
aggregates

----


> Add support for deferred computation for group window aggregates
> ----------------------------------------------------------------
>
>                 Key: FLINK-6969
>                 URL: https://issues.apache.org/jira/browse/FLINK-6969
>             Project: Flink
>          Issue Type: New Feature
>          Components: Table API & SQL
>            Reporter: Fabian Hueske
>            Assignee: sunjincheng
>
> Deferred computation is a strategy to deal with late arriving data and avoid 
> updates of previous results. Instead of computing a result as soon as it is 
> possible (i.e., when a corresponding watermark was received), deferred 
> computation adds a configurable amount of slack time in which late data is 
> accepted before the result is compute. For example, instead of computing a 
> tumbling window of 1 hour at each full hour, we can add a deferred 
> computation interval of 15 minute to compute the result quarter past each 
> full hour.
> This approach adds latency but can reduce the number of update esp. in use 
> cases where the user cannot influence the generation of watermarks. It is 
> also useful if the data is emitted to a system that cannot update result 
> (files or Kafka). The deferred computation interval should be configured via 
> the {{QueryConfig}}.



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