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https://issues.apache.org/jira/browse/CALCITE-7104?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18009417#comment-18009417
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Julian Hyde commented on CALCITE-7104:
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Please describe the feature more fully. What metadata is used to determine that
columns hold the same value? What planner rule is doing this transformation?
Also please improve the summary. Duplicate sort keys would be “order by x, x”,
and we already do that.
> Remove duplicate sort keys
> --------------------------
>
> Key: CALCITE-7104
> URL: https://issues.apache.org/jira/browse/CALCITE-7104
> Project: Calcite
> Issue Type: Improvement
> Reporter: weihua zhang
> Priority: Major
> Labels: pull-request-available
>
> {code:sql}
> select d1 from (select deptno as d1, deptno as d2 from dept ) as tmp order
> by d1, d2;
> {code}
> {noformat}
> LogicalProject(D1=[$0]), id = 2284
> LogicalSort(sort0=[$0], sort1=[$1], dir0=[ASC], dir1=[ASC]), id = 2283
> LogicalProject(D1=[$0], D2=[$0]), id = 2282
> LogicalTableScan(table=[[default, dept]]), id = 2278
> {noformat}
> LogicalSort can change to:
> {noformat}
> LogicalProject(D1=[$0]), id = 2284
> LogicalSort(sort0=[$0], dir0=[ASC]), id = 2283
> LogicalProject(D1=[$0], D2=[$0]), id = 2282
> LogicalTableScan(table=[[default, dept]]), id = 2278
> {noformat}
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