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From "Pawel Szczur (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (BEAM-315) Flink Runner compares keys unencoded which may produce incorrect results
Date Thu, 02 Jun 2016 08:50:59 GMT

    [ https://issues.apache.org/jira/browse/BEAM-315?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15311940#comment-15311940
] 

Pawel Szczur edited comment on BEAM-315 at 6/2/16 8:50 AM:
-----------------------------------------------------------

I thought about it. From your description I guess this should not be a real problem. As long
as the corresponding values are compared using the same comparison function. In fact I think
this was done on purpose to speed up the execution. 

First the values are shuffled according to hash function of the key and all the KV ends up
in a correct buckets, then we need to sort them. I guess we compare encoded keys because there's
no guarantee that pure keys have comparator defined and we have predefined bytes comparator.


was (Author: pawelszczur@gmail.com):
I thought about it. From your description I guess this should not be a real problem. As long
as the corresponding values are compared. In fact I think this was done on purpose to speed
up the execution. 

First the values are shuffled according to hash function of the key and all the KV ends up
in a correct buckets, then we need to sort them. I guess we compare encoded keys because there's
no guarantee that pure keys have comparator defined and we have predefined bytes comparator.

> Flink Runner compares keys unencoded which may produce incorrect results
> ------------------------------------------------------------------------
>
>                 Key: BEAM-315
>                 URL: https://issues.apache.org/jira/browse/BEAM-315
>             Project: Beam
>          Issue Type: Bug
>          Components: runner-flink
>    Affects Versions: 0.1.0-incubating
>            Reporter: Pawel Szczur
>            Assignee: Aljoscha Krettek
>         Attachments: CoGroupPipelineStringKey.java
>
>
> Same keys are processed multiple times.
> A repo to reproduce the bug:
> https://github.com/orian/cogroup-wrong-grouping
> Discussion:
> http://mail-archives.apache.org/mod_mbox/incubator-beam-user/201605.mbox/%3CCAB2uKkG2xHsWpLFUkYnt8eEzdxU%3DB_nu6crTwVi-ZuUpugxkPQ%40mail.gmail.com%3E
> Notice: I haven't tested other runners (didn't manage to configure Spark).



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