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https://issues.apache.org/jira/browse/HADOOP-3702?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alejandro Abdelnur updated HADOOP-3702:
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Attachment: patch3702.txt
Inverted precedence of configuration.
The chain element JobConf configuration has precedence over the chain job
JobConf.
This allows to set some defaults at chain job JobConf level and override them
at chain element level.
Note that this does not break anything at runtime as ll the injected
configuration for the task is used at the Chain{Mapper,Reducer}
> 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, 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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