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https://issues.apache.org/jira/browse/CALCITE-4634?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17356623#comment-17356623
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Julian Hyde edited comment on CALCITE-4634 at 6/3/21, 5:51 PM:
---------------------------------------------------------------
Do you claim that your proposed behavior benefits Calcite even if the goal is
not to generate SQL for SQL Server?
was (Author: julianhyde):
Do you claim that this behavior benefits Calcite even if the goal is not to
generate SQL for SQL Server?
> 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
> Priority: Major
>
> *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:
> {noformat}
> Each GROUP BY expression must contain at least one column that is not an
> outer reference.
> {noformat}
> 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.
> {noformat}
> SELECT 'abc' FROM table_name GROUP BY ('abc')
> {noformat}
> will be translated to:
> {noformat}
> SELECT 'abc' FROM table_name GROUP BY () having count(*)>0
> {noformat}
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