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https://issues.apache.org/jira/browse/CALCITE-6038?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
LakeShen updated CALCITE-6038:
------------------------------
Description:
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:
was:
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:
> 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
> Reporter: LakeShen
> Priority: Major
>
> 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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