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https://issues.apache.org/jira/browse/CALCITE-6038?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17772700#comment-17772700
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Julian Hyde commented on CALCITE-6038:
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The idea is a good one. I just don't think you're explaining it well. You
should remove all references to 'one' because it's not a magic number.
> Add optimization to remove redundant TopN when its input's row number is less
> or equal to one
> ---------------------------------------------------------------------------------------------
>
> Key: CALCITE-6038
> URL: https://issues.apache.org/jira/browse/CALCITE-6038
> Project: Calcite
> Issue Type: New Feature
> Reporter: LakeShen
> Priority: Major
>
> In Calcite , the TopN is represented by `Sort`,when a TopN's input source max
> row count is less or equal to 1,then we could remove the redundant TopN.
> For example,the sql:
> {code:java}
> SELECT count(*) FROM orders ORDER BY 1 LIMIT 10 {code}
> because the `SELECT count(*) FROM orders ` row count is 1, then we could
> remove `ORDER BY 1 LIMIT 10 `,after the optimization:
> {code:java}
> SELECT count(*) FROM orders {code}
> Above logic are same as Presto/Trino's
> [RemoveRedundantTopN|https://github.com/prestodb/presto/blob/21ab1ea2425e4bc65532ab156c60333e5a72dd09/presto-main/src/main/java/com/facebook/presto/sql/planner/iterative/rule/RemoveRedundantTopN.java#L27C1-L28C34]
> rule:
>
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