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https://issues.apache.org/jira/browse/CALCITE-7242?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18032766#comment-18032766
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weihua zhang commented on CALCITE-7242:
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[~julianhyde] Thanks. Yes. I will gradually add more test cases in the future.
Since I'm currently not familiar with the Calcite codebase, I'm making progress
through gradual iterations.
> Implement a rule to eliminate LITERAL_AGG so that other databases can handle
> it
> -------------------------------------------------------------------------------
>
> Key: CALCITE-7242
> URL: https://issues.apache.org/jira/browse/CALCITE-7242
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: weihua zhang
> Priority: Major
> Labels: pull-request-available
>
> Calcite can create an Aggregate RelNode with LITERAL_AGG AggregateCall to
> check for existence in a subquery. In this case, the Aggregate will do a
> group by, and just spit out a literal value for each row.
> The LITERAL_AGG function does not exist in other databases. In order to
> create a RelNode structure that other databases supports, this Aggregate is
> turned into an Aggregate that still does the "group by" on the relevant
> groups, but places a Project RelNode on top that returns the literal value.
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