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https://issues.apache.org/jira/browse/MAPREDUCE-5221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13703078#comment-13703078
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Tsuyoshi OZAWA commented on MAPREDUCE-5221:
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bq. 1. From the looks of it, the Reporter passed to MergeManagerImpl
constructor can only be a TaskReporter. For this patch, it should be okay to
typecast it unconditionally. With the current if condition, it is easy to
wonder how the combine works for Reporters which are not TaskReporter.
This is for some test cases which pass Reporter.NULL to MergeManagerImpl(e.g.
TestMerger#testInMemoryMerger). Do you think should we fix this test case?
bq. 2. Consequently, may be in a different JIRA, we should use
Reporter/TaskReporter uniform everywhere - ShufflePlugin, MergeManagerImpl, and
CombinerRunner.
I agree with uniforming Reporter/TaskReporter. I think we should do this in
differenct JIRA.
bq. Other than that, the patch looks good to me. Should we close this other
JIRAs as duplicates?
OK, I did it.
> 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, MAPREDUCE-5221.5.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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