[jira] [Created] (CALCITE-4634) Improve AggregateProjectPullUpConstantsRule to remove all constant keys

["Yingyu (Jira)" <ji...@apache.org>]

Yingyu created CALCITE-4634:
-------------------------------

             Summary: Improve AggregateProjectPullUpConstantsRule to remove all constant keys
                 Key: CALCITE-4634
                 URL: https://issues.apache.org/jira/browse/CALCITE-4634
             Project: Calcite
          Issue Type: Improvement
          Components: core
    Affects Versions: 1.16.0
            Reporter: Yingyu


AggregateProjectPullUpConstantsRule removes constant keys from an Aggregate. However, this rules never removes the last column, because Aggregate([]) returns 1 row even if its input is empty. 

The problem is if the remaining last column is a constant, it will fail on SQL Server with this error:
"Each GROUP BY expression must contain at least one column that is not an outer reference."
 
To improve on this we can improve the AggregateProjectPullUpConstantsRule to:
- Remove all constant keys from an Aggregate
- When no GROUP BY column is left, add a filter to the Aggregate([]) so that it returns empty dataset if its input is empty. 
 
E.g. 
select 'abc' from table_name group by ('abc')
will be translated to:
select 'abc' from table_name group by () having count(*) > 0



--
This message was sent by Atlassian Jira
(v8.3.4#803005)