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https://issues.apache.org/jira/browse/CALCITE-6891?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17935754#comment-17935754
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Julian Hyde commented on CALCITE-6891:
--------------------------------------
This rule will only do the right thing under CBO if LogicalIntersect has a cost
function that gives a lower cost if smaller inputs are first. Does it currently
have such a cost function?
> Implement IntersectReorderRule
> ------------------------------
>
> Key: CALCITE-6891
> URL: https://issues.apache.org/jira/browse/CALCITE-6891
> Project: Calcite
> Issue Type: Improvement
> Reporter: Zhen Chen
> Assignee: Zhen Chen
> Priority: Major
>
> Do we need this rule?
> from:
>
> {code:java}
> LogicalIntersect(all=[false])
> LogicalProject(DEPTNO=[$7])
> LogicalFilter(condition=[>($7, 10)])
> LogicalTableScan(table=[[CATALOG, SALES, EMP(big)]])
> LogicalProject(DEPTNO=[$0])
> LogicalFilter(condition=[>($0, 5)])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT(small)]]){code}
> to
>
>
> {code:java}
> LogicalIntersect(all=[false])
> LogicalProject(DEPTNO=[$0])
> LogicalFilter(condition=[>($0, 5)])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT(small)]])
> LogicalProject(DEPTNO=[$7])
> LogicalFilter(condition=[>($7, 10)])
> LogicalTableScan(table=[[CATALOG, SALES, EMP(big)]]) {code}
> This rule put smaller inputs first. This helps reduce the size of
> intermediate results.
>
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