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https://issues.apache.org/jira/browse/MAPREDUCE-5221?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13733146#comment-13733146
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Tsuyoshi OZAWA commented on MAPREDUCE-5221:
-------------------------------------------
bq. With the current if condition, it is easy to wonder how the combine works
for Reporters which are not TaskReporter.
I added comments to avoid the misunderstanding as follows:
<code>
+ // FIXME: This is a workaround to avoid typecast error
+ // by being given Reporter.NULL as reporter in a test case
+ // (e.g. TestMerger#testInMemoryMerger).
+ // Basically, reporter is an instance of Task.TaskReporter.
</code>
Additionally, I noticed that 1. and 2. in the [~kkambatl]'s comments are
related, and I think we should deal with these problems in another JIRA.
Thoughts?
> 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,
> MAPREDUCE-5221.6.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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