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https://issues.apache.org/jira/browse/HIVE-15580?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15832383#comment-15832383
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Xuefu Zhang commented on HIVE-15580:
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Thanks, Chao! I will commit this first and create a couple of followups.
[~lirui], it would be great if you can also take a look at the patch. I will
incorporate your comments (if any) as followups as well. Thanks.
> Eliminate unbounded memory usage for orderBy and groupBy in Hive on Spark
> -------------------------------------------------------------------------
>
> Key: HIVE-15580
> URL: https://issues.apache.org/jira/browse/HIVE-15580
> Project: Hive
> Issue Type: Improvement
> Components: Spark
> Reporter: Xuefu Zhang
> Assignee: Xuefu Zhang
> Attachments: HIVE-15580.1.patch, HIVE-15580.1.patch,
> HIVE-15580.2.patch, HIVE-15580.2.patch, HIVE-15580.3.patch,
> HIVE-15580.4.patch, HIVE-15580.5.patch, HIVE-15580.patch
>
>
> Currently, orderBy (sortBy) and groupBy in Hive on Spark uses unbounded
> memory. For orderBy, Hive accumulates key groups using ArrayList (described
> in HIVE-15527). For groupBy, Hive currently uses Spark's groupByKey operator,
> which has a shortcoming of not being able to spill to disk within a key
> group. Thus, for large key group, memory usage is also unbounded.
> It's likely that this will impact performance. We will profile and optimize
> afterwards. We could also make this change configurable.
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