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https://issues.apache.org/jira/browse/CALCITE-2648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16736313#comment-16736313
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Julian Hyde commented on CALCITE-2648:
--------------------------------------

Yes. That is what Volcano does. That is why Volcano is powerful.

The challenge is to rein in that power by pruning/prioritizing the order in 
which we traverse the search space.

> Output collation of EnumerableWindow is not consistent with its implementation
> ------------------------------------------------------------------------------
>
>                 Key: CALCITE-2648
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2648
>             Project: Calcite
>          Issue Type: Bug
>    Affects Versions: 1.17.0
>            Reporter: Hongze Zhang
>            Assignee: Julian Hyde
>            Priority: Major
>
> Here is a case:
> {code:sql}
> select x, COUNT(*) OVER (PARTITION BY x) from (values (20), (35)) as t(x) 
> ORDER BY x
> {code}
> Final plan:
> {code:java}
> EnumerableWindow(window#0=[window(partition {0} order by [] range between 
> UNBOUNDED PRECEDING and UNBOUNDED FOLLOWING aggs [COUNT()])])
>   EnumerableValues(tuples=[[{ 20 }, { 35 }]])
> {code}
> Output rows:
> {code:java}
> X  |EXPR$1 |
> ---|-------|
> 35 |1      |
> 20 |1      |
> {code}
> EnumerableWindow is supposed to preserve input collations, as a result 
> EnumerableSort is ignored. However the implementation of EnumerableWindow 
> generates non-ordered output (when PARTITION BY clause is used).



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