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https://issues.apache.org/jira/browse/MAPREDUCE-4891?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arun C Murthy resolved MAPREDUCE-4891.
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Resolution: Duplicate
Duplicate of MAPREDUCE-4808
> Pluggable merge at reduce side
> ------------------------------
>
> Key: MAPREDUCE-4891
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-4891
> Project: Hadoop Map/Reduce
> Issue Type: New Feature
> Affects Versions: 3.0.0
> Reporter: Jerry Chen
> Original Estimate: 504h
> Remaining Estimate: 504h
>
> The current implementation of sort in MapReduce is cooperated by Map side
> sort and Reduce side merge. MAPREDUCE-2454 provided pluggable sort at the
> Map side currently and pluggable shuffle at Reduce side, while no pluggable
> merger provided.
> Considering a general need of hash grouping and join, we may need to replace
> both the Map Sort and Reduce merge with a more light weight hash grouping
> alorithm. A general pluggable merge would help support this need.
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