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https://issues.apache.org/jira/browse/CALCITE-4557?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17326069#comment-17326069
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Haisheng Yuan commented on CALCITE-4557:
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I don't think it is necessary to simplify "ORDER BY deptno, empno, hiredate" to
"Emp ORDER BY deptno, empno", because the comparison in SORT operator will stop
at "empno" anyway, given that empno is unique.
> Sort costing should account the number of sort keys: the more keys to
> compare, the more the cost
> ------------------------------------------------------------------------------------------------
>
> Key: CALCITE-4557
> URL: https://issues.apache.org/jira/browse/CALCITE-4557
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.26.0
> Reporter: Vladimir Sitnikov
> Priority: Major
>
> Current costing for sort does not account for the number of keys in the
> comparison function which might result in worse plan selection.
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