Julian Hyde created CALCITE-4649:
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Summary: Add AggregateExpandGroupingSetsRule, a planner rule that
removes GROUPING SETS
Key: CALCITE-4649
URL: https://issues.apache.org/jira/browse/CALCITE-4649
Project: Calcite
Issue Type: Bug
Reporter: Julian Hyde
Add {{class AggregateExpandGroupingSetsRule}}, a planner rule that removes
{{GROUPING SETS}}.
Some databases do not support {{GROUPING SETS}}. (For example, BigQuery
supports {{GROUP BY ROLLUP}} but not general {{GROUPING SETS}}.) But {{GROUPING
SETS}} is a useful construct, increasingly used in user SQL, and also generated
by rules (e.g. {{AggregateExpandWithinDistinctRule}}).
The proposed rule would match an {{Aggregate}} whose {{groupSets}} field has
more than one element, and would convert it to an {{Aggregate}} over a {{Join}}
whose right-hand side is a list of integers, the group ids active in the query.
Calls to the {{GROUP_ID}} field would be replaced by references to the group id
column.
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