Yingyu created CALCITE-4634:
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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
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