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Date: Fri, 15 Nov 2013 02:11:22 +0000 (UTC)
From: "Ted Xu (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
Message-ID: <JIRA.12677954.1383814315208.78364.1384481482888@arcas>
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Subject: [jira] [Commented] (HIVE-5771) Constant propagation optimizer for
 Hive
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    [ https://issues.apache.org/jira/browse/HIVE-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13823214#comment-13823214 ] 

Ted Xu commented on HIVE-5771:
------------------------------

Eric, thank you for your comment. 

Yes, the constant propagate is an logical plan optimizer so it will process before vectorization process. But I'm not sure how constant folding can benefit vectorized execution. If there is anything I can do to improve it please let me know, thanks!

I created a review request here: https://reviews.apache.org/r/15561/

> 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: HIVE-5771.patch, 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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