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https://issues.apache.org/jira/browse/CALCITE-7242?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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weihua zhang updated CALCITE-7242:
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    Description: 
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.

  was:
Calcite can create an Aggregate RelNode with a single 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.


> Implement a rule to get rid of the LITERAL_AGG into other database can handle
> -----------------------------------------------------------------------------
>
>                 Key: CALCITE-7242
>                 URL: https://issues.apache.org/jira/browse/CALCITE-7242
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>            Reporter: weihua zhang
>            Priority: Major
>
> 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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