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https://issues.apache.org/jira/browse/HADOOP-3226?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Owen O'Malley updated HADOOP-3226:
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Release Note: Previously, the combiner was run exactly once on each record
by the map task. Now, the combiner may be run multiple times as the map's
output is sorted and merged. Additionally, it may be run on the reduce side as
data is merged. (was: Added run of the combiner on the map side merge if there
are more than min.num.spills.for.combine (3 by default), and run of the
combiner on the reduce-side spills. )
Hadoop Flags: [Incompatible change, Reviewed] (was: [Reviewed,
Incompatible change])
> Run combiner when merging spills from map output
> ------------------------------------------------
>
> Key: HADOOP-3226
> URL: https://issues.apache.org/jira/browse/HADOOP-3226
> Project: Hadoop Core
> Issue Type: Improvement
> Reporter: Chris Douglas
> Assignee: Chris Douglas
> Fix For: 0.18.0
>
> Attachments: 3226-0.patch, 3226-1.patch, 3226-2.patch, 3226-3.patch
>
>
> When merging spills from the map, running the combiner should further
> diminish the volume of data we send to the reduce.
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