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https://issues.apache.org/jira/browse/MAPREDUCE-3252?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13134606#comment-13134606
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Hudson commented on MAPREDUCE-3252:
-----------------------------------
Integrated in Hadoop-Mapreduce-0.23-Commit #47 (See
[https://builds.apache.org/job/Hadoop-Mapreduce-0.23-Commit/47/])
MAPREDUCE-3252. Fix map tasks to not rewrite data an extra time when map
output fits in spill buffer. Contributed by Todd Lipcon.
todd : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1188423
Files :
* /hadoop/common/branches/branch-0.23/hadoop-mapreduce-project/CHANGES.txt
*
/hadoop/common/branches/branch-0.23/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapred/MapTask.java
> MR2: Map tasks rewrite data once even if output fits in sort buffer
> -------------------------------------------------------------------
>
> Key: MAPREDUCE-3252
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-3252
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2, task
> Affects Versions: 0.23.0
> Reporter: Todd Lipcon
> Assignee: Todd Lipcon
> Priority: Critical
> Fix For: 0.23.0
>
> Attachments: mr-3252.txt, mr-3252.txt
>
>
> I found that, even if the output of a map task fits entirely in its sort
> buffer, it was rewriting the output entirely rather than just renaming the
> first spill into place. This is due to RawLocalFileSystem.rename() falling
> back to a copy if renameTo() fails. The first rename attempt was failing
> because no one has called mkdir for the output directory yet.
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