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https://issues.apache.org/jira/browse/CALCITE-2329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16757643#comment-16757643
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Vineet Garg commented on CALCITE-2329:
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bq. The "more optimal plan" pushes the "deptno=2" filter further towards the
table scan, whereas the original plan has it as a join condition
That make sense. I was looking at the overall plan which should be same as
EXISTS (without aggregate) according to "Since join condition is actually a
filter condition, it will be pushed into the filter during further planning
stages and join with the true condition is left."
> Enhance SubQueryRemoveRule to rewrite IN operator with the constant from the
> left side more optimally
> -----------------------------------------------------------------------------------------------------
>
> Key: CALCITE-2329
> URL: https://issues.apache.org/jira/browse/CALCITE-2329
> Project: Calcite
> Issue Type: Improvement
> Reporter: Volodymyr Vysotskyi
> Assignee: Julian Hyde
> Priority: Major
> Fix For: 1.17.0
>
>
> Currently, for queries like this:
> {code:sql}
> select sal from emp where 2 IN (select deptno from dept)
> {code}
> SubQueryRemoveRule rules expand query plan in such a way:
> {noformat}
> LogicalProject(SAL=[$5])
> LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],
> SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
> LogicalJoin(condition=[=(2, $9)], joinType=[inner])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> LogicalProject(DEPTNO=[$0])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> {noformat}
> Since join condition is actually a filter condition, it will be pushed into
> the filter during further planning stages and join with the true condition is
> left.
> But these types of the queries may be rewritten in the same way as EXISTS
> queries:
> {code:sql}
> select sal from emp where EXISTS (select deptno from dept where deptno=2)
> {code}
> with the more optimal plan:
> {noformat}
> LogicalProject(SAL=[$5])
> LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],
> SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
> LogicalJoin(condition=[true], joinType=[inner])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> LogicalAggregate(group=[{0}])
> LogicalProject(i=[true])
> LogicalFilter(condition=[=($0, 2)])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> {noformat}
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