[jira] [Commented] (FLINK-3869) WindowedStream.apply with FoldFunction is too restrictive

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-3869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15276122#comment-15276122 ] 

ASF GitHub Bot commented on FLINK-3869:
---------------------------------------

GitHub user aljoscha opened a pull request:

    https://github.com/apache/flink/pull/1973

    [FLINK-3869] Relax window fold generic parameters

    Before, the WindowFunction in a fold/apply could not emit a type that
    was different from the accumulator type of the fold. This restriction is
    unnecessary.

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

    $ git pull https://github.com/aljoscha/flink window-fold-relax

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

    https://github.com/apache/flink/pull/1973.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 #1973
    
----
commit 0e0d9b79b770d9708935920014314e4021e9751e
Author: Aljoscha Krettek <al...@gmail.com>
Date:   2016-05-05T06:34:44Z

    [FLINK-3869] Relax window fold generic parameters
    
    Before, the WindowFunction in a fold/apply could not emit a type that
    was different from the accumulator type of the fold. This restriction is
    unnecessary.

----


> WindowedStream.apply with FoldFunction is too restrictive
> ---------------------------------------------------------
>
>                 Key: FLINK-3869
>                 URL: https://issues.apache.org/jira/browse/FLINK-3869
>             Project: Flink
>          Issue Type: Improvement
>          Components: Streaming
>            Reporter: Aljoscha Krettek
>            Assignee: Aljoscha Krettek
>
> Right now we have this signature:
> {code}
> public <R> SingleOutputStreamOperator<R> apply(R initialValue, FoldFunction<T, R> foldFunction, WindowFunction<R, R, K, W> function) {
> {code}
> but we should have this signature to allow users to return a type other than the fold accumulator type from their window function:
> {code}
> public <ACC, R> SingleOutputStreamOperator<R> apply(ACC initialValue, FoldFunction<T, ACC> foldFunction, WindowFunction<ACC, R, K, W> function) {
> {code}



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