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https://issues.apache.org/jira/browse/HIVE-8017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14126674#comment-14126674
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Rui Li commented on HIVE-8017:
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[~xuefuz], spark doesn't guarantee order for group-by queries. And the hash
code of BytesWrtiable and HiveKey are computed differently. So the records
produced by the mappers are likely to be partitioned to different reducers. I
believe that's why we got different results (only different in order) after the
change.
I don't quite get the point of your last comment. I did try adding {{--
SORT_BEFORE_DIFF}} in the q file. It just seems the test framework is a little
particular about where we should put it (the test failed to run if I put it
before the {{set}} commands in the q file).
[~brocknoland] do you have any comments as how to use the {{--
SORT_BEFORE_DIFF}} label?
> Use HiveKey instead of BytesWritable as key type of the pair RDD [Spark
> Branch]
> -------------------------------------------------------------------------------
>
> Key: HIVE-8017
> URL: https://issues.apache.org/jira/browse/HIVE-8017
> Project: Hive
> Issue Type: Sub-task
> Components: Spark
> Reporter: Rui Li
> Assignee: Rui Li
> Attachments: HIVE-8017-spark.patch
>
>
> HiveKey should be used as the key type because it holds the hash code for
> partitioning. While BytesWritable serves partitioning well for simple cases,
> we have to use {{HiveKey.hashCode}} for more complicated ones, e.g. join,
> bucketed table, etc.
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