[jira] [Commented] (HIVE-8435) Add identity project remover optimization

["Pengcheng Xiong (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HIVE-8435?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14192973#comment-14192973 ] 

Pengcheng Xiong commented on HIVE-8435:
---------------------------------------

Initially I expect this patch can help me solve the external/internal name problem for groupby index when CBO is turned on. However, it seems that it does not work for a simple query even without index. :)

A query to show that it does not work:

select key, count(key) 
from src
group by key;
set hive.cbo.enable=true;
select key, count(key)
from src
group by key;

> Add identity project remover optimization
> -----------------------------------------
>
>                 Key: HIVE-8435
>                 URL: https://issues.apache.org/jira/browse/HIVE-8435
>             Project: Hive
>          Issue Type: New Feature
>          Components: Logical Optimizer
>    Affects Versions: 0.9.0, 0.10.0, 0.11.0, 0.12.0, 0.13.0
>            Reporter: Ashutosh Chauhan
>            Assignee: Sergey Shelukhin
>         Attachments: HIVE-8435.02.patch, HIVE-8435.03.patch, HIVE-8435.03.patch, HIVE-8435.04.patch, HIVE-8435.05.patch, HIVE-8435.05.patch, HIVE-8435.06.patch, HIVE-8435.1.patch, HIVE-8435.patch
>
>
> In some cases there is an identity project in plan which is useless. Better to optimize it away to avoid evaluating it without any benefit at runtime.



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