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Posted to dev@crunch.apache.org by "Matthias Friedrich (JIRA)" <ji...@apache.org> on 2012/07/21 14:15:35 UTC

[jira] [Commented] (CRUNCH-22) Join functions break when non-mapped types are used as a join key

    [ https://issues.apache.org/jira/browse/CRUNCH-22?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13419811#comment-13419811 ] 

Matthias Friedrich commented on CRUNCH-22:
------------------------------------------

Does anybody know the reason for Hadoop's object pooling? MR applications are typically I/O-bound so garbage collector overhead shouldn't matter much. I'm just curious, I've seen lots of bugs because of this.
                
> Join functions break when non-mapped types are used as a join key
> -----------------------------------------------------------------
>
>                 Key: CRUNCH-22
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-22
>             Project: Crunch
>          Issue Type: Bug
>            Reporter: Gabriel Reid
>            Assignee: Gabriel Reid
>             Fix For: 0.3.0
>
>         Attachments: CRUNCH-22.patch
>
>
> When non-mapped types (i.e. custom Writables or Avro records) are used as a join key in all join functions, the join does not operate correctly (and becomes closer to producing a Cartesian product) due to object re-use in Hadoop.

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