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https://issues.apache.org/jira/browse/HIVE-20153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16560102#comment-16560102
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Szehon Ho commented on HIVE-20153:
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Thanks Aihua for the fix. Yes I can test it, I am out of town at the moment so
need to wait to get back, and hope I can do it sometime next week. If you dont
want to wait, feel free to go ahead, I can comment my findings afterwards.
> Count and Sum UDF consume more memory in Hive 2+
> ------------------------------------------------
>
> Key: HIVE-20153
> URL: https://issues.apache.org/jira/browse/HIVE-20153
> Project: Hive
> Issue Type: Bug
> Components: UDF
> Affects Versions: 2.3.2
> Reporter: Szehon Ho
> Assignee: Aihua Xu
> Priority: Major
> Attachments: HIVE-20153.1.patch, Screen Shot 2018-07-12 at 6.41.28
> PM.png
>
>
> While playing with Hive2, we noticed that queries with a lot of count() and
> sum() aggregations run out of memory on Hadoop side where they worked before
> in Hive1.
> In many queries, we have to double the Mapper Memory settings (in our
> particular case mapreduce.map.java.opts from -Xmx2000M to -Xmx4000M), it
> makes it not so easy to upgrade to Hive 2.
> Taking heap dump, we see one of the main culprit is the field 'uniqueObjects'
> in GeneraicUDAFSum and GenericUDAFCount, which was added to support Window
> functions.
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