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https://issues.apache.org/jira/browse/SPARK-12770?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Reynold Xin updated SPARK-12770:
--------------------------------
    Description: 
There are a few things we can do:

1. If the first branch's condition is a true literal, remove the CaseWhen and 
use the value from that branch.

2. If a branch's condition is a false or null literal, remove that branch.

3. If only the else branch is left, remove the CaseWhen and use the value from 
the else branch.



  was:
There are a few things we can do:

1. If a branch's condition is a true literal, remove the CaseWhen and use the 
value from that branch.

2. If a branch's condition is a false or null literal, remove that branch.

3. If only the else branch is left, remove the CaseWhen and use the value from 
the else branch.




> Implement rules for branch elimination for CaseWhen in SimplifyConditionals
> ---------------------------------------------------------------------------
>
>                 Key: SPARK-12770
>                 URL: https://issues.apache.org/jira/browse/SPARK-12770
>             Project: Spark
>          Issue Type: Sub-task
>          Components: Optimizer, SQL
>            Reporter: Reynold Xin
>
> There are a few things we can do:
> 1. If the first branch's condition is a true literal, remove the CaseWhen and 
> use the value from that branch.
> 2. If a branch's condition is a false or null literal, remove that branch.
> 3. If only the else branch is left, remove the CaseWhen and use the value 
> from the else branch.



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