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From "Owen O'Malley (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-2) Reused Keys and Values fail with a Combiner
Date Thu, 30 Mar 2006 19:29:27 GMT
     [ http://issues.apache.org/jira/browse/HADOOP-2?page=all ]

Owen O'Malley updated HADOOP-2:
-------------------------------

    Attachment: clone-map-output.patch

This patch clones the keys and values before they are cached in the CombiningCollector.
It adds a new method named WritableUtils.clone(Writable, JobConf) that copies the the given
Writable.

> Reused Keys and Values fail with a Combiner
> -------------------------------------------
>
>          Key: HADOOP-2
>          URL: http://issues.apache.org/jira/browse/HADOOP-2
>      Project: Hadoop
>         Type: Bug
>   Components: mapred
>     Reporter: Owen O'Malley
>     Assignee: Owen O'Malley
>      Fix For: 0.1
>  Attachments: clone-map-output.patch
>
> If the map function reuses the key or value by destructively modifying it after the output.collect(key,value)
call and your application uses a combiner, the data is corrupted by having lots of instances
with the last key or value.

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