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https://issues.apache.org/jira/browse/MAPREDUCE-5221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13691165#comment-13691165
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Tsuyoshi OZAWA commented on MAPREDUCE-5221:
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[~kkambatl], I understood what you mean correctly. I explain why I choose the
current design.
bq. I thought all of MAPREDUCE-5221, MAPREDUCE-5294 and MAPREDUCE-5295 are
related and motivated by the same bug (from the description) that reduce-side
combiner is not called using the new API.
That's right.
bq. IIUC, we could just use an if condition similar to the one in my previous
comment, and that should solve the issue and we don't need the other two JIRAs.
No? Am I missing something?
No, there are a missing point.
The sequence of running combiner is different between old API and new API.
Task#CombinerRunner class abstracts it, so I choosed to reuse it in
MAPREDUCE-5294. Do you think we don't use it?
The patch for MAPREDUCE-5221 and MAPREDUCE-5295 just removes needless arguments
or adds tests. Should we merge these patches into one patch?
> Reduce side Combiner is not used when using the new API
> -------------------------------------------------------
>
> Key: MAPREDUCE-5221
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-5221
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Affects Versions: 2.0.4-alpha
> Reporter: Siddharth Seth
> Assignee: Tsuyoshi OZAWA
> Attachments: MAPREDUCE-5221.1.patch, MAPREDUCE-5221.2.patch,
> MAPREDUCE-5221.3.patch, MAPREDUCE-5221.4.patch
>
>
> If a combiner is specified using o.a.h.mapreduce.Job.setCombinerClass - this
> will silently ignored on the reduce side since the reduce side usage is only
> aware of the old api combiner.
> This doesn't fail the job - since the new combiner key does not deprecate the
> old key.
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