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https://issues.apache.org/jira/browse/CALCITE-5717?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17724766#comment-17724766
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Benchao Li commented on CALCITE-5717:
-------------------------------------
By saying "prune", I meant to drop the Aggregate totally, not prune fields of
the Aggregate.
I understand the difference of "select 1 from emps group by ()" and "select
distinct 1 from emps", and it seems not affect this optimization, I'll update
the description to add more details about the proposal.
> Prune Project's input if project has no InputRef and the input has 1 row
> ------------------------------------------------------------------------
>
> Key: CALCITE-5717
> URL: https://issues.apache.org/jira/browse/CALCITE-5717
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Benchao Li
> Assignee: Benchao Li
> Priority: Major
> Labels: pull-request-available
>
> The idea is to improve SQL
> {code:sql}
> select 1 from emps group by ()
> {code}
> In this case, we can safely prune the Aggregate.
> This idea is brought up in the discussion of CALCITE-5506
> We can add this improvement to ProjectAggregateMergeRule
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