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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-1664) Forbid sorting on POJOs
Date Fri, 27 Mar 2015 23:42:52 GMT

    [ https://issues.apache.org/jira/browse/FLINK-1664?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14384904#comment-14384904

ASF GitHub Bot commented on FLINK-1664:

GitHub user fhueske opened a pull request:


    [FLINK-1664] Adds checks if selected sort key is sortable

    - Adds checks if a sort key can be actually sorted. 
      - The POJO type is defined as non-sortable, because an order would depend on the undefined
order of POJO fields. 
    - Adds a few more tests for API sort functions

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

    $ git pull https://github.com/fhueske/flink sortOnPojo

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


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

    This closes #541
commit e26d934eb1b2c14298900c53e8413487ce43a17a
Author: Fabian Hueske <fhueske@apache.org>
Date:   2015-03-27T20:37:59Z

    [FLINK-1664] Adds check if a selected sort key is sortable


> Forbid sorting on POJOs
> -----------------------
>                 Key: FLINK-1664
>                 URL: https://issues.apache.org/jira/browse/FLINK-1664
>             Project: Flink
>          Issue Type: Bug
>          Components: JobManager
>    Affects Versions: 0.8.0, 0.9
>            Reporter: Fabian Hueske
>            Assignee: Fabian Hueske
> Flink's groupSort, partitionSort, and outputSort operators allow to sort partitions or
groups of a DataSet.
> If the sort is defined on a POJO field, the sort order is not well defined. Internally,
the POJO is recursively decomposed into atomic fields (primitives or generic types) and sorted
by sorting these atomic fields. Thereby, the order of these atomic fields is not well defined
(I believe it is lexicographic order of the POJO's member names).
> IMO, the best approach is to forbid sorting on POJO types for now. Instead, it is always
possible to select the nested fields of the POJO that should be used for sorting. Later we
can relax this restriction.

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