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https://issues.apache.org/jira/browse/CALCITE-7252?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18040557#comment-18040557
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Alessandro Solimando commented on CALCITE-7252:
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Not having reached an agreement on a specific solution (possibly for lack of
time from the reviewers) doesn't mean the proposal itself should be discarded,
I don't think nobody objects that this is an interesting optimization, even if
all the details on where and how to implement it optimally haven't been
clarified.
> Implement ORDER BY Optimization Using Functional Dependencies at SQL-to-Rel
> Conversion Phase
> --------------------------------------------------------------------------------------------
>
> Key: CALCITE-7252
> URL: https://issues.apache.org/jira/browse/CALCITE-7252
> Project: Calcite
> Issue Type: New Feature
> Reporter: Zhen Chen
> Assignee: Zhen Chen
> Priority: Minor
> Labels: pull-request-available
>
> This issue implements an optimization that removes redundant columns from
> ORDER BYclauses based on functional dependencies (FDs) during the
> SQL-to-Relational (SQL-to-Rel) conversion process. This approach was chosen
> because a rule-based implementation within the Volcano planner would face
> significant hurdles with trait satisfaction. Specifically, an optimized
> collation (e.g., [0]) cannot satisfy the original, broader collation
> requirement (e.g., [0, 1]) under the standard trait subsumption check, which
> would prevent the optimizer from selecting the more efficient plan, details
> see CALCITE-7234.
> The implementation achieves the following results:
> {code:java}
> -- Original Query (FD: empno(primary key) -> sal)
> select empno, sal from emp order by empno, sal;
> -- Optimized Logical Plan
> LogicalSort(sort0=[$0], dir0=[ASC]) <-- Instead of sort0=[$0], sort1=[$1]
> LogicalProject(EMPNO=[$0], SAL=[$5])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]]) {code}
> Introduces a new optimizeOrderBy configuration parameter to enable the
> optimization. The default value is false.
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