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https://issues.apache.org/jira/browse/CALCITE-3399?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated CALCITE-3399:
------------------------------------
    Labels: pull-request-available  (was: )

> RelFieldTrimmer trim fields for UNION, INTERSECT, INTERSECT ALL, EXCEPT, 
> EXCEPT ALL
> -----------------------------------------------------------------------------------
>
>                 Key: CALCITE-3399
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3399
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>            Reporter: jin xing
>            Assignee: jin xing
>            Priority: Major
>              Labels: pull-request-available
>
> *RelFieldTrimmer#trimFields* provides functionality to trim fields for  
> *UNION, UNION ALL, INTERSECT, INTERSECT ALL, EXCEPT, EXCEPT ALL;*
> But *UNION ALL, INTERSECT, INTERSECT ALL, EXCEPT, EXCEPT ALL* works by 
> checking duplication. Column pruning on inputs of *SetOp* might lead to 
> different semantics.
>  
> Take below example for illustration
> {code:java}
> emp0:
> name, deptno
>  "A",   0
>  "B",   1
> emp1:
> name, deptno
>  "C",   0
>  "D",   2
> select deptno from
> (select name, deptno from emp0
> intersect
> select name, deptno from emp1)
> {code}
> Run above Sql on emp0 and emp1, result is not empty if trim fields on inputs 
> of INTERSECT, but result is empty if DO NOT trim fields on inputs of INTERSECT



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