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https://issues.apache.org/jira/browse/CALCITE-844?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14709543#comment-14709543
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Sean Hsuan-Yi Chu commented on CALCITE-844:
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[~julianhyde] Can you help review? Thanks!
> The lack of Project under LogicalWindow hurts the performance
> -------------------------------------------------------------
>
> Key: CALCITE-844
> URL: https://issues.apache.org/jira/browse/CALCITE-844
> Project: Calcite
> Issue Type: Bug
> Reporter: Sean Hsuan-Yi Chu
> Assignee: Sean Hsuan-Yi Chu
>
> Firstly of all, this issue happens when HepPlanner is used with
> ProjectToWindowRule.PROJECT rule.
> A simple query like:
> {code}
> select sum(deptno) over(partition by deptno) as sum1
> from emp
> {code}
> produces
> {code}
> LogicalProject($0=[$9])
> LogicalWindow(window#0=[window(partition {7} order by [] range between
> UNBOUNDED PRECEDING and UNBOUNDED FOLLOWING aggs [SUM($7)])])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
> However, from performance standpoint, it is better to have a project between
> LogicalWindow and LogicalTableScan since only one column is used.
> Interestingly, when there is an expression in the window function. For
> example,
> {code}
> select sum(deptno + 1) over(partition by deptno) as sum1
> from emp"
> {code}
> produces
> {code}
> LogicalProject($0=[$2])
> LogicalWindow(window#0=[window(partition {0} order by [] range between
> UNBOUNDED PRECEDING and UNBOUNDED FOLLOWING aggs [SUM($1)])])
> LogicalProject(DEPTNO=[$7], $1=[+($7, 1)])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
> The LogicalProject below window can trim out useless columns or even be
> pushed into Scan, which is very important optimization Calcite can exploit.
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