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Posted to issues@hive.apache.org by "Xuefu Zhang (JIRA)" <ji...@apache.org> on 2016/03/16 14:51:33 UTC
[jira] [Commented] (HIVE-13293) Query occurs performance
degradation after enabling parallel order by for Hive on sprak
[ https://issues.apache.org/jira/browse/HIVE-13293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15197341#comment-15197341 ]
Xuefu Zhang commented on HIVE-13293:
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Yes, the result can vary from query to query due to the cost of a separate sampling spark job. I'd image that the benefit diminishes as the data to be processed get smaller.
While we are here, [~Lifeng Wang], could you check if SamplingOptimizer, which does the similar thing for MR, also has the same effect for MapReduce engine? Thanks.
> Query occurs performance degradation after enabling parallel order by for Hive on sprak
> ---------------------------------------------------------------------------------------
>
> Key: HIVE-13293
> URL: https://issues.apache.org/jira/browse/HIVE-13293
> Project: Hive
> Issue Type: Bug
> Components: Spark
> Affects Versions: 2.0.0
> Reporter: Lifeng Wang
>
> I use TPCx-BB to do some performance test on Hive on Spark engine. And found query 10 has performance degradation when enabling parallel order by.
> It seems that sampling cost much time before running the real query.
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