Jiajun Xie created CALCITE-6201:
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Summary: Merge Aggregate node if count distinct column has been
deduplicated
Key: CALCITE-6201
URL: https://issues.apache.org/jira/browse/CALCITE-6201
Project: Calcite
Issue Type: Improvement
Components: core
Reporter: Jiajun Xie
Assignee: Jiajun Xie
distinct column is redundant because count has distinct.
{code:java}
select count(distinct x) cnt
from(
select distinct sal x from emp
) t {code}
PlanBefore is
{noformat}
LogicalAggregate(group=[{}], CNT=[COUNT(DISTINCT $0)])
LogicalAggregate(group=[{5}])
LogicalTableScan(table=[[CATALOG, SALES, EMP]]){noformat}
PlanAfter should be
{noformat}
LogicalAggregate(group=[{}], CNT=[COUNT(DISTINCT $5)])
LogicalTableScan(table=[[CATALOG, SALES, EMP]]){noformat}
But `CoreRules.AGGREGATE_MERGE` not support it, we can improve it.
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