Fix a wrong results bug with count over an aggregation that had a mix of global and non-global grouping sets.
We were not checking for single global aggregations correctly in QueryCardinalityUtil, so we would return that the plan was scalar if there were any empty grouping sets rather than if the empty grouping set was the only grouping set. we have now fixed this to return that if all of the grouping sets are global, then the cardinality will be the number of grouping sets, and otherwise it is at least the number of global grouping sets.
This fixes queries like the following:
SELECT COUNT(*) FROM (SELECT count(*) FROM tpch.sf1.nation GROUP BY GROUPING SETS (nationkey, ()));
previously we would incorrectly return 1. And now we return 26.
This change may also fix bugs with correlated subqueries, as those also use the isScalar() utility function.
Fixes wrong results for queries with counts over mixed global and grouped aggregations .e.g. SELECT COUNT(*) FROM (SELECT count(*) FROM tpch.sf1.nation GROUP BY GROUPING SETS (nationkey, ()));
== RELEASE NOTES ==
General Changes
* Fix a bug where count queries on top of aggregations with mixed global and grouped grouping sets could return wrong results.
Description
Fix a wrong results bug with count over an aggregation that had a mix of global and non-global grouping sets.
We were not checking for single global aggregations correctly in QueryCardinalityUtil, so we would return that the plan was scalar if there were any empty grouping sets rather than if the empty grouping set was the only grouping set. we have now fixed this to return that if all of the grouping sets are global, then the cardinality will be the number of grouping sets, and otherwise it is at least the number of global grouping sets.
This fixes queries like the following:
previously we would incorrectly return 1. And now we return 26.
This change may also fix bugs with correlated subqueries, as those also use the isScalar() utility function.
Motivation and Context
Fixes https://github.com/prestodb/presto/issues/22977
Impact
Fixes wrong results for queries with counts over mixed global and grouped aggregations .e.g.
SELECT COUNT(*) FROM (SELECT count(*) FROM tpch.sf1.nation GROUP BY GROUPING SETS (nationkey, ()));
Test Plan
added unit tests
Contributor checklist
Release Notes
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