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https://issues.apache.org/jira/browse/HIVE-949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12783198#action_12783198
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Zheng Shao commented on HIVE-949:
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This transaction might increase the amount of memory and objects created per
distinct key.
HIVE-535 has a proposal that should save both CPU time (mainly object creation
time), and memory space.
> Object deepCopy in GroupBy Operator
> -----------------------------------
>
> Key: HIVE-949
> URL: https://issues.apache.org/jira/browse/HIVE-949
> Project: Hadoop Hive
> Issue Type: Improvement
> Reporter: Ning Zhang
> Assignee: He Yongqiang
> Fix For: 0.5.0
>
> Attachments: hive-949-2009-11-26.patch
>
>
> In GroupByOperator, objects are first deep copied and then check whether or
> not the object is in the hash table (in hash-mode aggregation). In fact,
> object deep copy could be very expensive (around 5% CPU time). A simple
> change could be generate the object without deep copy through ObjectInspector
> and check its existence in the hash table. If not exists, we call deep copy.
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