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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-5771) Constant propagation optimizer for Hive
Date Thu, 14 Nov 2013 17:41:21 GMT

    [ https://issues.apache.org/jira/browse/HIVE-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13822655#comment-13822655
] 

Xuefu Zhang commented on HIVE-5771:
-----------------------------------

[~tedxu] Thank you for your patch. Please rename the patch according to the convention so
that test can run, something like HIVE-5771.patch, HIVE-5771.1.patch, and so on.

> Constant propagation optimizer for Hive
> ---------------------------------------
>
>                 Key: HIVE-5771
>                 URL: https://issues.apache.org/jira/browse/HIVE-5771
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Ted Xu
>            Assignee: Ted Xu
>         Attachments: constprog_default_true.patch
>
>
> Currently there is no constant folding/propagation optimizer, all expressions are evaluated
at runtime. 
> HIVE-2470 did a great job on evaluating constants on UDF initializing phase, however,
it is still a runtime evaluation and it doesn't propagate constants from a subquery to outside.
> It may reduce I/O and accelerate process if we introduce such an optimizer.



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