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https://issues.apache.org/jira/browse/CALCITE-3015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16824874#comment-16824874
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Chunwei Lei commented on CALCITE-3015:
--------------------------------------
Makes sense. Thanks [~zabetak].
> Add rule to remove constants in group keys
> ------------------------------------------
>
> Key: CALCITE-3015
> URL: https://issues.apache.org/jira/browse/CALCITE-3015
> Project: Calcite
> Issue Type: Improvement
> Reporter: Chunwei Lei
> Assignee: Chunwei Lei
> Priority: Major
> Fix For: 1.20.0
>
>
> Constants in group keys can be removed to reduce shuffle. For instance,
>
> {code:java}
> select key, count(*) from (select 1 as key from src) dual group by key;
> {code}
> can be reduced to
> {code:java}
> select count(*) from (select 1 as key from src) dual;{code}
> It could save much resource in distribute system if all group keys are
> constants since the distribution becomes {{SINGLETON}} instead of {{HASH}}.
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