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https://issues.apache.org/jira/browse/HIVE-13293?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15197341#comment-15197341
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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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