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https://issues.apache.org/jira/browse/CALCITE-7104?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18009481#comment-18009481
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Zhen Chen commented on CALCITE-7104:
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I think it is better to use it as a rule, similar to RelFieldTrimmer, which is
too heavy. By implementing a utility class to recursively detect whether the
expression is repeated, and then the rule uses this utility class to
independently handle SORT (or possibly AGG).
> 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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