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https://issues.apache.org/jira/browse/CALCITE-1990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16288617#comment-16288617
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LeoWangLZ commented on CALCITE-1990:
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Thanks [~julianhyde], Thank for your test cases and guava's Orderings
> Make RelDistribution extend RelMultipleTrait
> --------------------------------------------
>
> Key: CALCITE-1990
> URL: https://issues.apache.org/jira/browse/CALCITE-1990
> Project: Calcite
> Issue Type: Bug
> Reporter: LeoWangLZ
> Assignee: Julian Hyde
> Fix For: 1.15.0
>
> Original Estimate: 0.2h
> Remaining Estimate: 0.2h
>
> In Distributed System, RelDistribution is used for Exchange or SortExchange.
> for some operators it may deliver RelDistribution Trait, but some operator
> like SortedMergeJoin may deliver multiple traits.
> eg:
> {code:java}
> Query:
> select * from T1 join T2 on T1.c1=T2.d1;
> Suppose Plan:
> SortedMergeJoin
> Exchange(c1)
> T1(c1)
> Exchange(d1)
> T2(d1)
> {code}
> than SortedMergeJoin can deliver RelDistribution(hash\[c1\]) or
> RelDistribution(hash\[d1\]).
> we can consider RelDistribution extend RelMultipleTrait like RelCollation.
> EnumerableMergeJoin is the case for RelCollation, and RelDistribution is also
> fit for SortedMergeJoin in Distributed system
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