[jira] [Commented] (FLINK-758) Add count method to DataSet and implement CountOperator

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[jira] [Commented] (FLINK-758) Add count method to DataSet and implement CountOperator

Shang Yuanchun (Jira)

    [ https://issues.apache.org/jira/browse/FLINK-758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14032295#comment-14032295 ]

ASF GitHub Bot commented on FLINK-758:
--------------------------------------

Github user fhueske commented on the pull request:

    https://github.com/apache/incubator-flink/pull/20#issuecomment-46162167
 
    We don't need the initial value for GroupReduce ( != grouped Reduce).
    If an initial value is required for GroupReduce, it can be coded in the GroupReduceFunction.


> Add count method to DataSet and implement CountOperator
> -------------------------------------------------------
>
>                 Key: FLINK-758
>                 URL: https://issues.apache.org/jira/browse/FLINK-758
>             Project: Flink
>          Issue Type: Improvement
>            Reporter: GitHub Import
>              Labels: github-import
>             Fix For: pre-apache
>
>         Attachments: pull-request-758-7518001488867571817.patch
>
>
> At the request of @twalthr. This is the count operator I've implemented some time ago to get the to know the new Java API. It introduces `DataSet.count()`, which is executed as a map (to ones) and reduce (sum up the ones). I initially didn't do the PR, because of the following problem: empty DataSets don't work as the first map won't have any input to operate on.
> If more people think that we should include this operator we can think about a possible solution to the problem.
> ---------------- Imported from GitHub ----------------
> Url: https://github.com/stratosphere/stratosphere/pull/758
> Created by: [uce|https://github.com/uce]
> Labels: enhancement, java api,
> Milestone: Release 0.6 (unplanned)
> Created at: Tue May 06 10:42:33 CEST 2014
> State: open



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