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https://issues.apache.org/jira/browse/CALCITE-4050?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17128493#comment-17128493
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Rui Wang edited comment on CALCITE-4050 at 6/8/20, 6:06 PM:
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Yes it is valid. To solve it, the tricky part is to improve Mapping to allow 
1->n mapping (and inverse() also handles it properly). Right now the 
implementation uses a int[] as internal data structure. 


was (Author: amaliujia):
Yes it is valid. To solve it, the tricky part is to improve Mapping to allow 
1->n mapping (and inverse() also handles it properly). Right now Mappings uses 
a int[] as internal data structure. 

> Traits Propagation for EnumerableMergeJoin Produces Incorrect Result
> --------------------------------------------------------------------
>
>                 Key: CALCITE-4050
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4050
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Jinpeng Wu
>            Priority: Major
>
> In EnumerableMergeJoin's deriveTraits method, it uses a Map to record mapping 
> from left keys to right keys (the keyMap variable). However, the left keys 
> could have duplicate entries. 
>  One example is JdbcTest.testJoinInCorrelatedSubQuery, the expected plan is
> EnumerableProject(deptno=[$0], name=[$1], employees=[$2], location=[$3])
>   EnumerableMergeJoin(condition=[AND(=($0, $5), =($0, $4))], joinType=[inner])
>     EnumerableSort(sort0=[$0], dir0=[ASC])
>       EnumerableTableScan(table=[[hr, depts]])
>     EnumerableSort(sort0=[$1], sort1=[$0], dir0=[ASC], dir1=[ASC])
>       ...
> where left keys are [0, 0] , and right keys are [1, 0]. Deriving right 
> child's traits may result in incorrect output.



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