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https://issues.apache.org/jira/browse/HIVE-9644?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14529124#comment-14529124
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Gopal V commented on HIVE-9644:
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[~ashutoshc]: added to my review queue, thanks!
> CASE comparison operator rotation optimization
> ----------------------------------------------
>
> Key: HIVE-9644
> URL: https://issues.apache.org/jira/browse/HIVE-9644
> Project: Hive
> Issue Type: Bug
> Components: Logical Optimizer
> Affects Versions: 0.14.0, 1.0.0, 1.1.0
> Reporter: Gopal V
> Assignee: Ashutosh Chauhan
> Attachments: HIVE-9644.1.patch, HIVE-9644.patch
>
>
> Constant folding for queries don't kick in for some automatically generated
> query patterns which look like this.
> {code}
> hive> explain select count(1) from store_sales where (case ss_sold_date when
> '1998-01-01' then 1 else null end)=1;
> {code}
> This should get rewritten by pushing the equality into the case branches.
> {code}
> select count(1) from store_sales where (case ss_sold_date when '1998-01-01'
> then 1=1 else null=1 end);
> {code}
> Ending up with a simplified filter condition, resolving itself as
> {code}
> select count(1) from store_sales where ss_sold_date= '1998-01-01' ;
> {code}
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