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https://issues.apache.org/jira/browse/CALCITE-5894?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17750952#comment-17750952
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Benchao Li commented on CALCITE-5894:
-------------------------------------
In actual physical implementation, if the first field has already know the
order, you do not need to compare the second field. So, my question is, how
much improvement may this bring, does it deserve a dedicated rule for this
optimization?
> Add SortRemoveRedundantRule to remove redundant sort fields if sort fields
> contains unique key
> ----------------------------------------------------------------------------------------------
>
> Key: CALCITE-5894
> URL: https://issues.apache.org/jira/browse/CALCITE-5894
> Project: Calcite
> Issue Type: New Feature
> Reporter: JingDas
> Assignee: JingDas
> Priority: Minor
>
> In some scene, Sort fields can be reduct, if sort fields contain unique key
> For Example
> {code:java}
> SELECT name, Emp.salary FROM Emp
> order by empno, ename{code}
> where `empno` is a key, `ename` is redundant since `empno` alone is
> sufficient to determine the order of any two records.
> So the SQL can be optimized as following:
> {code:java}
> SELECT name, Emp.salary FROM Emp
> order by empno{code}
> Sorting is an expensive operation, however. Therefore, it is imperative that
> sorting
> is optimized to avoid unnecessary sort field.
>
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