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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-949) Object deepCopy in GroupBy Operator
Date Tue, 24 Nov 2009 02:46:42 GMT

    [ https://issues.apache.org/jira/browse/HIVE-949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12781752#action_12781752
] 

Namit Jain commented on HIVE-949:
---------------------------------

Also, get some performance numbers for this

> 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
>
> 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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