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https://issues.apache.org/jira/browse/CALCITE-1990?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16175338#comment-16175338
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Julian Hyde commented on CALCITE-1990:
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The idea is OK in principle, but can you describe the impact of this change on
existing users? Would it be breaking? What tests would you add to make sure
this works fully?
> Make RelDistribution to extends RelMultipleTrait
> ------------------------------------------------
>
> Key: CALCITE-1990
> URL: https://issues.apache.org/jira/browse/CALCITE-1990
> Project: Calcite
> Issue Type: Bug
> Reporter: Rheet Wong
> Assignee: Julian Hyde
> 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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