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https://issues.apache.org/jira/browse/CALCITE-2948?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16827371#comment-16827371
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Danny Chan commented on CALCITE-2948:
-------------------------------------
[~hyuan] [~julianhyde]
I also think a rule match is more acceptable, but the rule implementation
severely depends on the RelNode's equivalence(mean what kinds of 2 RelNodes are
equavelent ?), which is a section that Calcite never touches. The only way i
can think is the node's digest, but i'm not very confident about it.
Another problem is that the SemiJoin removing needs info about whether the join
keys are unique to the datasource, which are not always provided.
It seems better that we generate a more simple plan at decorrelation the very
first time than to simplify a complex plan through rules. Cause there are
constraints like above.
> Complicated logical plan generated for in subquery with non-equi condition
> --------------------------------------------------------------------------
>
> Key: CALCITE-2948
> URL: https://issues.apache.org/jira/browse/CALCITE-2948
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Haisheng Yuan
> Assignee: Danny Chan
> Priority: Major
> Labels: pull-request-available, sub-query
> Time Spent: 1.5h
> Remaining Estimate: 0h
>
> Repro:
> Add the following test to SqlToRelConverterTest.java.
> {code:java}
> @Test public void testSubQueryIN() {
> final String sql = "select deptno\n"
> + "from EMP e\n"
> + "where deptno in (select deptno\n"
> + "from EMP where empno=e.empno+1)";
> sql(sql).ok();
> }
> {code}
> Plan:
> {code:java}
> LogicalProject(DEPTNO=[$7])
> LogicalJoin(condition=[AND(=($0, $10), =($7, $9))], joinType=[inner])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> LogicalAggregate(group=[{0, 1}])
> LogicalProject(DEPTNO=[$7], EMPNO0=[$9])
> LogicalJoin(condition=[=($0, +($9, 1))], joinType=[inner])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> LogicalProject(EMPNO=[$0])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {code}
> One join would suffice.
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