Julian Hyde created CALCITE-4154:
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Summary: Add a rule to merge a Project onto an Aggregate
Key: CALCITE-4154
URL: https://issues.apache.org/jira/browse/CALCITE-4154
Project: Calcite
Issue Type: Bug
Reporter: Julian Hyde
Add a rule to merge a {{Project}} onto an {{Aggregate}}. In practice, it means
that aggregate functions that are not used in the Project are removed from the
Aggregate.
For example,
{code:java}
SELECT deptno, sum_sal
FROM (
SELECT deptno, job, SUM(sal) AS sum_sal, MIN(ename) AS min_ename
FROM emp
GROUP BY deptno, job)
{code}
becomes
{code:java}
SELECT deptno, sum_sal
FROM (
SELECT deptno, job, SUM(sal) AS sum_sal
FROM emp
GROUP BY deptno, job)
{code}
Note that {{min_ename}} is removed from the {{Aggregate}} (because it is not
used by the {{Project}}). {{job}} is not used, but it remains because it is a
{{GROUP BY}} key.
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