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https://issues.apache.org/jira/browse/CALCITE-2554?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16737156#comment-16737156
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Michael Mior commented on CALCITE-2554:
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[~zabetak] Slipped my mind. Thanks for the reminder!
> Enrich enumerable join operators with order preserving information
> ------------------------------------------------------------------
>
> Key: CALCITE-2554
> URL: https://issues.apache.org/jira/browse/CALCITE-2554
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.17.0
> Reporter: Stamatis Zampetakis
> Assignee: Michael Mior
> Priority: Minor
> Labels: pull-request-available
> Fix For: 1.19.0
>
>
> Calcite enumerable convention offers four ways to perform a join over two
> inputs:
> # EnumerableJoin
> # EnumerableThetaJoin
> # EnumerableSemiJoin
> # EnumerableCorrelate
> The algorithms that are used by the afforementioned operators :
> # org.apache.calcite.linq4j.EnumerableDefaults#join_
> # org.apache.calcite.linq4j.EnumerableDefaults#thetaJoin
> # org.apache.calcite.linq4j.EnumerableDefaults#semiJoin
> # org.apache.calcite.linq4j.EnumerableDefaults#correlateJoin
> in many cases can preserves the order of the left (outer) input. However,
> this information is not reflected in the RelTraitSet and thus cannot be
> exploited by the optimizer. Without this information, sort operators
> following the join cannot be removed (using SortRemoveRule) leading to
> suboptimal plans.
>
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