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From "Zoltan Haindrich (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-20557) Constant Folding: null > (expr) is not constant folded to NULL
Date Fri, 14 Sep 2018 11:57:00 GMT

    [ https://issues.apache.org/jira/browse/HIVE-20557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16614695#comment-16614695
] 

Zoltan Haindrich commented on HIVE-20557:
-----------------------------------------

CALCITE-2555 will fix this

> Constant Folding: null > (expr) is not constant folded to NULL
> --------------------------------------------------------------
>
>                 Key: HIVE-20557
>                 URL: https://issues.apache.org/jira/browse/HIVE-20557
>             Project: Hive
>          Issue Type: Improvement
>          Components: CBO
>    Affects Versions: 3.1.0, 4.0.0
>            Reporter: Gopal V
>            Priority: Major
>
> {code}
> create temporary table foo(col1 int, col2 int, col3 int, col5 int, col9 int) stored as
orc;
> explain select count(1) from foo where 
> CASE WHEN (col5 is not null) THEN (((col1 / col5) > (col9 / col3))) ELSE ((null >
(col9 / col3))) END;
> explain select count(1), max((col9/col3) > null) from foo where 
> CASE WHEN (col5 is not null) THEN (((col1 / col5) > (col9 / col3))) ELSE (((col9 /
col3) > null)) END;
> {code}
> There's no sane way to write this query, but this is actually generated by CBO for an
expression which looks like 
> {code}
> case when t_w_firstyear.year_total > 0 then t_w_secyear.year_total / t_w_firstyear.year_total
else null end
>            > case when t_s_firstyear.year_total > 0 then t_s_secyear.year_total
/ t_s_firstyear.year_total else null end
> {code}



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