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https://issues.apache.org/jira/browse/PIG-841?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pradeep Kamath updated PIG-841:
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Summary: PERFORMANCE: The sample MR job in order by (or joins which require
sampling) implementation can use Hadoop sorting instead of doing a POSort
(was: PERFORMANCE: The sample MR job in order by implementation can use Hadoop
sorting instead of doing a POSort)
> PERFORMANCE: The sample MR job in order by (or joins which require sampling)
> implementation can use Hadoop sorting instead of doing a POSort
> --------------------------------------------------------------------------------------------------------------------------------------------
>
> Key: PIG-841
> URL: https://issues.apache.org/jira/browse/PIG-841
> Project: Pig
> Issue Type: Improvement
> Affects Versions: 0.2.1
> Reporter: Pradeep Kamath
> Fix For: 0.3.0
>
>
> Currently the sample map reduce job in order by implementation does the
> following:
> - sample 100 records from each map
> - group all on the above output
> - sort the output bag from the above grouping on keys of the order by
> - give the sorted bag to FindQuantiles udf
> The steps 2 and 3 above can be replaced by
> - group the sample output by the order by key and set parallelism of the
> group to 1 so that output of the group goes to one reducer. Since Hadoop
> ensures the output of the group is sorted by key we get sorting for free
> without using POSort
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