[jira] [Created] (CALCITE-4649) Add AggregateExpandGroupingSetsRule, a planner rule that removes GROUPING SETS

["Julian Hyde (Jira)" <ji...@apache.org>]

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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