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https://issues.apache.org/jira/browse/CALCITE-2658?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16679203#comment-16679203
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Chunwei Lei commented on CALCITE-2658:
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Thanks [~julianhyde]
I will create another jira to support creating Exchange and SortExchange in
RelBuilder.
> 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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