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