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https://issues.apache.org/jira/browse/CALCITE-2648?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16749959#comment-16749959
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Vladimir Sitnikov commented on CALCITE-2648:
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Just in case, PostgreSQL does not keep input collation when OVER expression is
present (note that if fails to eliminate the redundant sort, however it does
not matter much):
!postgresql_96_doesnt_care_to_keep_collation_for_project_over_expression.png!
> 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
> Attachments:
> postgresql_96_doesnt_care_to_keep_collation_for_project_over_expression.png
>
>
> 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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