Zhen Chen created CALCITE-7116:
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Summary: Optimize queries with GROUPING SETS by converting them
into equivalent UNION ALL of GROUP BY operations.
Key: CALCITE-7116
URL: https://issues.apache.org/jira/browse/CALCITE-7116
Project: Calcite
Issue Type: New Feature
Components: core
Reporter: Zhen Chen
Fix For: 1.41.0
Currently, GROUPING SETS operations may not be optimally executed in some
cases. This ticket proposes a rule to transform GROUPING SETS into a series of
UNION ALL operations, each with its own GROUP BY clause.
{code:java}
SELECT a, b, c FROM t GROUP BY GROUPING SETS ((a,b), (a,c))
{code}
{code:java}
SELECT a, b, NULL AS c FROM t GROUP BY a, b
UNION ALL
SELECT a, NULL AS b, c FROM t GROUP BY a, c
{code}
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