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From "Ted Xu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-5771) Constant propagation optimizer for Hive
Date Sun, 17 Nov 2013 13:31:23 GMT

    [ https://issues.apache.org/jira/browse/HIVE-5771?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13824834#comment-13824834
] 

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

Hi Eric,

Thank you for your reviewing. I already updated the diff file according to your suggestions.

With regard to timestamp literal and cast constants, this optimizer will fold them like other
primitive types. I tested timestamp and date, it look good to me. I'm sorry I haven't got
chance to merge the tests into HIVE-5771.1.patch. I will add them later.

> 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-5771.1.patch, HIVE-5771.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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