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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HIVE-15683) Measure performance impact on group by by HIVE-15580
Date Fri, 20 Jan 2017 21:28:26 GMT
Xuefu Zhang created HIVE-15683:
----------------------------------

             Summary: Measure performance impact on group by by HIVE-15580
                 Key: HIVE-15683
                 URL: https://issues.apache.org/jira/browse/HIVE-15683
             Project: Hive
          Issue Type: Improvement
          Components: Spark
    Affects Versions: 2.2.0
            Reporter: Xuefu Zhang
            Assignee: Xuefu Zhang


HIVE-15580 changed the way the data is shuffled for order by: instead of using Spark's groupByKey
to shuffle data, Hive on Spark now uses repartitionAndSortWithinPartitions(), which generates
(key, value) pairs instead of original (key, value iterator). This might have some performance
implications, but it's needed to get rid of unbound memory usage by {{groupByKey}}.

Here we'd like to compare group by performance with or w/o HIVE-15580. If the impact is significant,
we can provide a configuration that allows user to switch back to the original way of shuffling.

This work should be ideally done after HIVE-15682 as the optimization there should help the
performance here as well. 



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