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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-15580) Eliminate unbounded memory usage for orderBy and groupBy in Hive on Spark
Date Tue, 24 Jan 2017 19:02:29 GMT

    [ https://issues.apache.org/jira/browse/HIVE-15580?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15836414#comment-15836414
] 

Xuefu Zhang commented on HIVE-15580:
------------------------------------

Hi [~Ferd] and [~dapengsun], I'm wondering if you guys could help measure the performance
impact of the patch here? We at Uber don't have a dedicated environment, so getting accurate
measurement is challenging. It would be great if you guys can help. Based on the result, we
may have some followup work to do. 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
>             Fix For: 2.2.0
>
>         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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