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https://issues.apache.org/jira/browse/CALCITE-841?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14692608#comment-14692608
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Sean Hsuan-Yi Chu edited comment on CALCITE-841 at 8/12/15 12:19 AM:
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Interestingly, for the example provided above, if you flip the order in the 
select list, there would be only one LogicalWindow:
{code}
LogicalProject($0=[$3], $1=[$4])
  LogicalWindow(window#0=[window(partition {1} order by [0] range between 
UNBOUNDED PRECEDING and CURRENT ROW aggs [SUM($2), SUM($1)])])
    LogicalProject(SAL=[$5], DEPTNO=[$7], $2=[+($7, $7)])
      LogicalTableScan(table=[[CATALOG, SALES, EMP]])
{code}


was (Author: seanhychu):
Interestingly, for the example provided above, if you flip the order in the 
select list, there would be only one LogicalWindow:
{code}
LogicalProject(SUM1=[$0], SUM2=[$0])
  LogicalProject($0=[$3])
    LogicalWindow(window#0=[window(partition {1} order by [0] range between 
UNBOUNDED PRECEDING and CURRENT ROW aggs [SUM($2)])])
      LogicalProject(SAL=[$5], DEPTNO=[$7], $2=[+($7, $7)])
        LogicalTableScan(table=[[CATALOG, SALES, EMP]])
{code}

> When the argument of window functions is an expression, redundant windows 
> could be generated
> --------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-841
>                 URL: https://issues.apache.org/jira/browse/CALCITE-841
>             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 query with this pattern:
> {code}
> select fn(col) over w, fn(expr) over w
> from ...
> {code}
> will generate two "LogicalWindow" even if we have only an identical window 
> frame.
> For example, 
> {code}
> select sum(deptno) over(partition by deptno order by sal) as sum1, 
> sum(deptno + deptno) over(partition by deptno order by sal) as sum2
> from emp
> {code}
> gives:
> {code}
> LogicalProject($0=[$2], $1=[$4])
>   LogicalWindow(window#0=[window(partition {1} order by [0] range between 
> UNBOUNDED PRECEDING and CURRENT ROW aggs [SUM($3)])])
>     LogicalProject(SAL=[$0], DEPTNO=[$1], $2=[$2], $3=[+($1, $1)])
>       LogicalProject(SAL=[$5], DEPTNO=[$7], $2=[$9])
>         LogicalWindow(window#0=[window(partition {7} order by [5] range 
> between UNBOUNDED PRECEDING and CURRENT ROW aggs [SUM($7)])])
>           LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}



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