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https://issues.apache.org/jira/browse/CALCITE-6038?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17774225#comment-17774225
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Julian Hyde commented on CALCITE-6038:
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I changed the summary from "Remove redundant TopN when its input's row count is
provably at most one row." to "Remove 'Limit n' when the input is guaranteed to
never return more than 'n' rows".
('TopN' is only used by a few dialects. Summaries should not end in '.'.
Generalize 'one' to 'N'.)
> Remove redundant TopN when its input's row count is provably at most one row.
> -----------------------------------------------------------------------------
>
> Key: CALCITE-6038
> URL: https://issues.apache.org/jira/browse/CALCITE-6038
> Project: Calcite
> Issue Type: New Feature
> Components: core
> Reporter: LakeShen
> Assignee: LakeShen
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.36.0
>
>
> In Calcite , the TopN is represented by `Sort`,when a TopN's input source row
> count is provably at most one row
> ,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, it is at most one
> row,then we could remove `ORDER BY 1 LIMIT 10 `,after the optimization,the
> sql is :
> {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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