[jira] [Created] (HIVE-20557) Constant Folding: null > (expr) is not constant folded to NULL

[Gopal V (JIRA)]

Gopal V created HIVE-20557:
------------------------------

             Summary: 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
            Reporter: Gopal V


{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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