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https://issues.apache.org/jira/browse/CALCITE-3952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17090994#comment-17090994
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Vineet Garg commented on CALCITE-3952:
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bq. Given a rel which emit at most 1 row (RelMetadataQuery.getRowCount<=1),
should RelMetadataQuery.collations(rel) match the Sort order
[~jinxing6...@126.com] I don't think it is necessary in this case for sort
order to match. If input is producing at most 1 row there is no need to sort.
> Improve SortRemoveRule to remove Sort based on rowcount
> -------------------------------------------------------
>
> Key: CALCITE-3952
> URL: https://issues.apache.org/jira/browse/CALCITE-3952
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Vineet Garg
> Assignee: Vineet Garg
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
> If a query is guaranteed to produce maximum one row it is safe to remove Sort
> (along with limit).
> Example:
> {code:sql}
> select count(*) cs from store_sales where ss_ext_sales_price > 100.00 order
> by cs limit 100
> {code}
> Although logically equivalent this can greatly benefit physical plans by
> removing extra operator and avoiding unnecessary data transfer.
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