Jiajun Xie created CALCITE-6240:
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Summary: Removed ROW_NUMBER if OVER PARTITION BY unique key
Key: CALCITE-6240
URL: https://issues.apache.org/jira/browse/CALCITE-6240
Project: Calcite
Issue Type: Improvement
Components: core
Reporter: Jiajun Xie
Assignee: Jiajun Xie
The SQL Only have ROW_NUMBER function.
{code:java}
SELECT empno, ename FROM (
SELECT ROW_NUMBER() OVER (PARTITION BY empno) rn, empno, ename
FROM emp
) WHERE rn <= 5{code}
to
{code:java}
SELECT empno, ename FROM emp{code}
If we know every partition count is less than filter count, we can optimize
{code:java}
SELECT deptno, ename FROM (
SELECT ROW_NUMBER() OVER (PARTITION BY deptno) rn, deptno, ename
FROM emp
) WHERE rn <= N
-- Statistic let we know every department count is less than N{code}
to
{code:java}
SELECT empno, ename FROM emp {code}
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