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https://issues.apache.org/jira/browse/CALCITE-4634?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Yingyu updated CALCITE-4634:
----------------------------
Description:
Optimizer rule *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.
An enhancement could be done to AggregateProjectPullUpConstantsRule so that it
removes all constant keys:
- Remove all constant keys from an Aggregate
- (Only)When no key is left from previous step (Aggregate becomes
Aggregate([])), 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}
was:
*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}
> 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
>
> Optimizer rule *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.
> An enhancement could be done to AggregateProjectPullUpConstantsRule so that
> it removes all constant keys:
> - Remove all constant keys from an Aggregate
> - (Only)When no key is left from previous step (Aggregate becomes
> Aggregate([])), 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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