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https://issues.apache.org/jira/browse/HADOOP-3702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12615633#action_12615633
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Alejandro Abdelnur commented on HADOOP-3702:
--------------------------------------------
Thanks for the feedback.
*On "each stage in the pipeline having its own configuration .. put them into
the outer configuration":*
The use case is that mappers/reducer in the chain (I'm not using 'pipe' to
avoid confusion as it has other use in Hadoop) are not aware of each other, and
that they are in a chain, and they may have collision in the configuration keys
they use.
*On "If you are going to do that, ... make Configuration Writable and use the
writable stringifier?":*
That was my initial idea but it would have required changes in the
Configuration and I was avoiding any change in the core.
I'll make this change.
*On "use {{hadoop.io.Data{In,Out}putBuffer}} ...":*
I'll look at it.
*On "You should probably convert the task id string to a TaskAttemptID ...":*
OK
*On "preferred sytle is Sun's":*
OK
> add support for chaining Maps in a single Map and after a Reduce [M*/RM*]
> -------------------------------------------------------------------------
>
> Key: HADOOP-3702
> URL: https://issues.apache.org/jira/browse/HADOOP-3702
> Project: Hadoop Core
> Issue Type: New Feature
> Components: mapred
> Environment: all
> Reporter: Alejandro Abdelnur
> Assignee: Alejandro Abdelnur
> Priority: Minor
> Attachments: patch3702.txt, patch3702.txt, patch3702.txt,
> patch3702.txt, patch3702.txt
>
>
> On the same input, we usually need to run multiple Maps one after the other
> without no Reduce. We also have to run multiple Maps after the Reduce.
> If all pre-Reduce Maps are chained together and run as a single Map a
> significant amount of Disk I/O will be avoided.
> Similarly all post-Reduce Maps can be chained together and run in the Reduce
> phase after the Reduce.
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