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https://issues.apache.org/jira/browse/CALCITE-7828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18130336#comment-18130336
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Yu Xu edited comment on CALCITE-7828 at 10/22/26, 2:08 PM:
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In many cases, we compare it with PostgreSQL; whether it returns empty results
in other databases requires further investigation.
was (Author: JIRAUSER307770):
https://onecompiler.com/oracle/456t3xmtf fails to produce any output; I’m not
entirely sure how things work in the Oracle environment.
> Aggregate whose grouping sets include () returns no rows on empty input
> -----------------------------------------------------------------------
>
> Key: CALCITE-7828
> URL: https://issues.apache.org/jira/browse/CALCITE-7828
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.42.0
> Reporter: Aleksandr Efimov
> Assignee: Yu Xu
> Priority: Major
> Labels: pull-request-available
>
> ROLLUP(a) is GROUPING SETS ((a), ()), and the () set yields one row even when
> the input is empty, as a query with no GROUP BY does (CALCITE-1059). Calcite
> returns no rows instead:
> {code:sql}
> SELECT a, COUNT(*) AS c FROM (VALUES (1)) AS t(a) WHERE FALSE GROUP BY
> ROLLUP(a);
> {code}
> The expected result is one row, (NULL, 0). CUBE(a, b) and GROUPING SETS ((a),
> ()) lose the row for () in the same way.
> Two places drop the row. {{PruneEmptyRules.AGGREGATE_INSTANCE}} replaces the
> aggregate with an empty {{Values}}, because its guard,
> {{Aggregate.isNotGrandTotal}}, only checks that the group count is greater
> than 0. With that rule removed, the plan keeps an {{EnumerableAggregate}}
> over the empty {{Values}}, but the query still returns no rows:
> {noformat}
> EnumerableAggregate(group=[{0}], groups=[[{0}, {}]], C=[COUNT()])
> EnumerableValues(tuples=[[]])
> {noformat}
> Reproduced on 1.42.0 and on main (4e9460600c).
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