Zhen Chen created CALCITE-7252:
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Summary: Implement ORDER BY Optimization Using Functional
Dependencies at SQL-to-Rel Conversion Phase
Key: CALCITE-7252
URL: https://issues.apache.org/jira/browse/CALCITE-7252
Project: Calcite
Issue Type: New Feature
Reporter: Zhen Chen
Assignee: Zhen Chen
This issue implements an optimization that removes redundant columns from ORDER
BYclauses based on functional dependencies (FDs) during the SQL-to-Relational
(SQL-to-Rel) conversion process. This approach was chosen because a rule-based
implementation within the Volcano planner would face significant hurdles with
trait satisfaction. Specifically, an optimized collation (e.g., [0]) cannot
satisfy the original, broader collation requirement (e.g., [0, 1]) under the
standard trait subsumption check, which would prevent the optimizer from
selecting the more efficient plan, details see CALCITE-7234.
The implementation achieves the following results:
{code:java}
-- Original Query (FD: empno(primary key) → sal)
select empno, sal from emp order by empno, sal;
-- Optimized Logical Plan
LogicalSort(sort0=[$0], dir0=[ASC]) <-- Instead of sort0=[$0], sort1=[$1]
LogicalProject(EMPNO=[$0], SAL=[$5])
LogicalTableScan(table=[[CATALOG, SALES, EMP]]) {code}
Introduces a new optimizeOrderBy configuration parameter to enable the
optimization. The default value is false.
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