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https://issues.apache.org/jira/browse/FLINK-838?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14087451#comment-14087451
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Artem Tsikiridis commented on FLINK-838:
----------------------------------------

Yes, I am talking about comparators to sort keys before reducing.

I do it by adding some functionality to {{WritableComparator}} of Flink. ( 
https://github.com/atsikiridis/incubator-flink/blob/sorting-hadoop/stratosphere-java/src/main/java/eu/stratosphere/api/java/typeutils/runtime/WritableComparator.java
 )

So far this comparator sorts in ascending order by default. Now it accepts a 
hadoop {{Comparator}} which it wraps.

And also I extended the api of {{WritableTypeInformation}} so when specifying 
the return types of {{HadoopMapFunction}}  one can set this custom hadoop 
comparator. I have tried some test cases (descending keys comparator, 
comparator by first letter etc.

> GSoC Summer Project: Implement full Hadoop Compatibility Layer for 
> Stratosphere
> -------------------------------------------------------------------------------
>
>                 Key: FLINK-838
>                 URL: https://issues.apache.org/jira/browse/FLINK-838
>             Project: Flink
>          Issue Type: Improvement
>            Reporter: GitHub Import
>              Labels: github-import
>             Fix For: pre-apache
>
>
> This is a meta issue for tracking @atsikiridis progress with implementing a 
> full Hadoop Compatibliltiy Layer for Stratosphere.
> Some documentation can be found in the Wiki: 
> https://github.com/stratosphere/stratosphere/wiki/%5BGSoC-14%5D-A-Hadoop-abstraction-layer-for-Stratosphere-(Project-Map-and-Notes)
> As well as the project proposal: 
> https://github.com/stratosphere/stratosphere/wiki/GSoC-2014-Project-Proposal-Draft-by-Artem-Tsikiridis
> Most importantly, there is the following **schedule**:
> *19 May - 27 June (Midterm)*
> 1) Work on the Hadoop tasks, their Context and the mapping of Hadoop's 
> Configuration to the one of Stratosphere. By successfully bridging the Hadoop 
> tasks with Stratosphere, we already cover the most basic Hadoop Jobs. This 
> can be determined by running some popular Hadoop examples on Stratosphere 
> (e.g. WordCount, k-means, join) (4 - 5 weeks)
> 2) Understand how the running of these jobs works (e.g. command line 
> interface) for the wrapper. Implement how will the user run them. (1 - 2 
> weeks).
> *27 June - 11 August*
> 1) Continue wrapping more "advanced" Hadoop Interfaces (Comparators, 
> Partitioners, Distributed Cache etc.) There are quite a few interfaces and it 
> will be a challenge to support all of them. (5 full weeks)
> 2) Profiling of the application and optimizations (if applicable)
> *11 August - 18 August*
> Write documentation on code, write a README with care and add more 
> unit-tests. (1 week)
> ---------------- Imported from GitHub ----------------
> Url: https://github.com/stratosphere/stratosphere/issues/838
> Created by: [rmetzger|https://github.com/rmetzger]
> Labels: core, enhancement, parent-for-major-feature, 
> Milestone: Release 0.7 (unplanned)
> Created at: Tue May 20 10:11:34 CEST 2014
> State: open



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