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https://issues.apache.org/jira/browse/FLINK-4937?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15659666#comment-15659666
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ASF GitHub Bot commented on FLINK-4937:
---------------------------------------

GitHub user sunjincheng121 opened a pull request:

    https://github.com/apache/flink/pull/2792

    Flink 4937 pr

    Thanks for contributing to Apache Flink. Before you open your pull request, 
please take the following check list into consideration.
    If your changes take all of the items into account, feel free to open your 
pull request. For more information and/or questions please refer to the [How To 
Contribute guide](http://flink.apache.org/how-to-contribute.html).
    In addition to going through the list, please provide a meaningful 
description of your changes.
    
    - [ √] General
      - The pull request references the related JIRA issue ("[FLINK-4937] Add 
incremental group window aggregation for streaming Table API")
      - 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
    
    - [ √] 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-4937-PR

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

    https://github.com/apache/flink/pull/2792.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 #2792
    
----
commit a5e80909037da38b1252eb301ec04bd38daa19c9
Author: 金竹 <jincheng.su...@alibaba-inc.com>
Date:   2016-11-12T10:55:07Z

    Add incremental group window aggregation for streaming Table API

commit 0753d3bd09b739233167c4d054c6580fb6a41194
Author: 金竹 <jincheng.su...@alibaba-inc.com>
Date:   2016-11-12T12:48:16Z

    Add TestProcessingTimeSlidingGroupWindowOverCountWithAVG

----


> Add incremental group window aggregation for streaming Table API
> ----------------------------------------------------------------
>
>                 Key: FLINK-4937
>                 URL: https://issues.apache.org/jira/browse/FLINK-4937
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>    Affects Versions: 1.2.0
>            Reporter: Fabian Hueske
>            Assignee: sunjincheng
>
> Group-window aggregates for streaming tables are currently not done in an 
> incremental fashion. This means that the window collects all records and 
> performs the aggregation when the window is closed instead of eagerly 
> updating a partial aggregate for every added record. Since records are 
> buffered, non-incremental aggregation requires more storage space than 
> incremental aggregation.
> The DataStream API which is used under the hood of the streaming Table API 
> features [incremental 
> aggregation|https://ci.apache.org/projects/flink/flink-docs-release-1.2/dev/windows.html#windowfunction-with-incremental-aggregation]
>  using a {{ReduceFunction}}.
> We should add support for incremental aggregation in group-windows.
> This is a follow-up task of FLINK-4691.



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