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https://issues.apache.org/jira/browse/CALCITE-3806?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde closed CALCITE-3806.
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Resolution: Invalid
Closing as "invalid" because this is a question, not a bug or a feature
request. It's a good question, but please ask it on the dev list.
> How to optimize repeated RelNode Structures ?
> ---------------------------------------------
>
> Key: CALCITE-3806
> URL: https://issues.apache.org/jira/browse/CALCITE-3806
> Project: Calcite
> Issue Type: Wish
> Components: core
> Reporter: anjali shrishrimal
> Priority: Minor
>
> Let's say input structure looks like this :
> {noformat}
> LogicalUnion(all=[true])
> LogicalProject(EMPNO=[$0])
> LogicalFilter(condition=[>=($0, 7369)])
> LogicalTableScan(table=[[scott, EMP]])
> LogicalProject(EMPNO=[$0])
> LogicalFilter(condition=[>=($0, 7369)])
> LogicalTableScan(table=[[scott, EMP]]){noformat}
>
> In this case,
> {noformat}
> LogicalProject(EMPNO=[$0])
> LogicalFilter(condition=[>=($0, 7369)])
> LogicalTableScan(table=[[scott, EMP]]){noformat}
> is repeated. It is going to fetch same data twice.
> Can we save one fetch? Can we somehow tell 2nd input of union to make use of
> union's 1st input. Is there any way to express that in plan?
>
> Also,
> If the structure was like this :
> {noformat}
> LogicalUnion(all=[true])
> LogicalProject(EMPNO=[$0])
> LogicalFilter(condition=[>=($0, 7369)])
> LogicalTableScan(table=[[scott, EMP]])
> LogicalProject(EMPNO=[$0])
> LogicalFilter(condition=[>=($0, 8000)])
> LogicalTableScan(table=[[scott, EMP]]){noformat}
> Second part of union can perform filtering on fetched data of 1st part. (As
> second's output is subset of first's output)
>
> Does calcite provide such kind of optimizations ?
> If not, what are the challenges to do so?
>
>
> I would appreciate some comments on this. Thank you.
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