Zoltan Haindrich created HIVE-21152:
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             Summary: Rewrite if expression to case and recognize simple case 
as an if
                 Key: HIVE-21152
                 URL: https://issues.apache.org/jira/browse/HIVE-21152
             Project: Hive
          Issue Type: Improvement
          Components: CBO
            Reporter: Zoltan Haindrich


* {{IF}} is not part of the sql standard; however given its special form its 
simpler - and currently in Hive it also has vectorized support
* there people writing standard sql may write: {{CASE WHEN member=1 THEN attr+1 
else attr+2 END}} which is essentially an if.

The idea is to rewrite IFs to CASEs for the cbo; and recognize simple "CASE"-s 
as IFs to get vectorization on them if possible





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