Gopal V created HIVE-9644:
-----------------------------

             Summary: Constant folding case for CASE/WHEN
                 Key: HIVE-9644
                 URL: https://issues.apache.org/jira/browse/HIVE-9644
             Project: Hive
          Issue Type: Bug
          Components: Logical Optimizer
    Affects Versions: 1.2.0
            Reporter: Gopal V


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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