[jira] [Created] (CALCITE-3256) Add ProjectOnProjectToProjectUnifyRule for materialization matching.

["jin xing (JIRA)" <ji...@apache.org>]

jin xing created CALCITE-3256:
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             Summary: Add ProjectOnProjectToProjectUnifyRule for materialization matching.
                 Key: CALCITE-3256
                 URL: https://issues.apache.org/jira/browse/CALCITE-3256
             Project: Calcite
          Issue Type: Improvement
          Components: core
            Reporter: jin xing
            Assignee: jin xing


In current implementation of rules in SubstitutionVisitor.java & MaterializedViewSubstitutionVisitor.java, it's quite common to add a compensating Project on top of child node of target(MV-rel) during matching. But afterwards the next round matching should be able to handle such a compensated Project and match upward along the plan tree. Otherwise we fail the matching. After all, the goal of matching is to transform the query and let a complete 'target' show up in the transformed query plan.

I found cases where the compensated Project cannot be properly handled.

{code:java}
MV:
select deptno, sum(salary) + 2, sum(commission)
from emps
group by deptno

Query:
select deptno, sum(salary) + 2
from emps
group by deptno
{code}

After matching of the Aggregates, a compensating Project is added, but afterwards matching fails to handle it.



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