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https://issues.apache.org/jira/browse/CALCITE-2658?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16682758#comment-16682758
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Chunwei Lei commented on CALCITE-2658:
--------------------------------------

Hi, [~julianhyde]
I have submitted an extra PR for introducing WindowReduceExpressionsRule at 
https://github.com/apache/calcite/pull/912. Please review it at your 
convenience.Thank you.

> Introducing more ReduceExpressionRules
> --------------------------------------
>
>                 Key: CALCITE-2658
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2658
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.17.0
>            Reporter: Chunwei Lei
>            Assignee: Julian Hyde
>            Priority: Major
>             Fix For: 1.18.0
>
>
> It is useful to have rules reducing Exchange/Sort/SortExchange keys, e.g.,
> SELECT key,value FROM (SELECT 1 AS key, value FROM src) r DISTRIBUTE BY key;
> can be reduced to 
> SELECT 1 AS key, value FROM src;    # Since singleton requirement may already 
> required by SELECT.
> SELECT key,value FROM (SELECT 1 AS key, value FROM src) r ORDER BY key;
> can be reduced to
> SELECT 1 AS key, value FROM src;    # Since ordering on constant is useless.



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