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Posted to dev@hive.apache.org by "Zheng Shao (JIRA)" <ji...@apache.org> on 2009/03/24 21:59:50 UTC
[jira] Commented: (HIVE-364) Hive Operators should calculate the
value of common expressions just once
[ https://issues.apache.org/jira/browse/HIVE-364?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12688865#action_12688865 ]
Zheng Shao commented on HIVE-364:
---------------------------------
Note that if an expression contains functions like rand(), it should not be shared and should be calculated separately.
> Hive Operators should calculate the value of common expressions just once
> -------------------------------------------------------------------------
>
> Key: HIVE-364
> URL: https://issues.apache.org/jira/browse/HIVE-364
> Project: Hadoop Hive
> Issue Type: Improvement
> Components: Serializers/Deserializers
> Reporter: Zheng Shao
>
> Currently, if we have "t.a + t.b" in 2 different expressions in the select clause / where clause, we are computing it twice.
> We should cache the value of the expression evaluation result to save CPU time.
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