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https://issues.apache.org/jira/browse/CALCITE-1493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15718502#comment-15718502
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Julian Hyde commented on CALCITE-1493:
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To be honest, I'm not sure whether that join is required, and it's very hard to
answer.
For this bug, can we please stick to the issue of whether the plan is correct,
not whether it is efficient. Can you figure out whether it is correct (i.e.
produces the correct results for all possible data). If it's not correct give a
data set that breaks it. If it is correct I will commit the fix.
> Wrong plan for NOT IN correlated queries
> ----------------------------------------
>
> Key: CALCITE-1493
> URL: https://issues.apache.org/jira/browse/CALCITE-1493
> Project: Calcite
> Issue Type: Bug
> Components: core
> Reporter: Vineet Garg
> Assignee: Julian Hyde
> Labels: sub-query
> Attachments: CALCITE-1493.test.patch
>
>
> Plan generated by calcite with SubqueryRemoveRule followed by de-correlation
> for the following query:
> {noformat} select sal from emp where empno NOT IN (select deptno from dept
> where emp.job = dept.name) {noformat}
> is
> {noformat}
> LogicalProject(SAL=[$5])
> LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],
> SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
> LogicalFilter(condition=[IS NULL($11)])
> LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3],
> HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8],
> DEPTNO0=[CAST($9):INTEGER], JOB0=[CAST($10):VARCHAR(10) CHARACTER SET
> "ISO-8859-1" COLLATE "ISO-8859-1$en_US$primary"], $f2=[CAST($11):BOOLEAN])
> LogicalJoin(condition=[AND(=($2, $10), =($0, $9))], joinType=[inner])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> LogicalProject(DEPTNO=[$0], JOB=[$1], $f2=[true])
> LogicalAggregate(group=[{0, 1}])
> LogicalProject(DEPTNO=[$0], JOB=[$2], i=[$1])
> LogicalProject(DEPTNO=[$0], i=[true], JOB=[$1])
> LogicalProject(DEPTNO=[$0], JOB=[$2])
> LogicalJoin(condition=[=($2, $1)], joinType=[inner])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> LogicalAggregate(group=[{0}])
> LogicalProject(JOB=[$2])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {noformat}
> As you can notice instead of doing Left Outer Join Calcite is doing Inner
> Join. This will produce wrong results.
> Plan for same query just before SubqueryRemove Rule is:
> {noformat}
> LogicalProject(SAL=[$5])
> LogicalFilter(condition=[NOT(IN($0, {
> LogicalProject(DEPTNO=[$0])
> LogicalFilter(condition=[=($cor0.JOB, $1)])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> }))], variablesSet=[[$cor0]])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> {noformat}
> Plan just after SubqueryRemove Rule:
> {noformat}
> LogicalProject(SAL=[$5])
> LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],
> SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
> LogicalFilter(condition=[IS NULL($10)])
> LogicalFilter(condition=[=($0, $9)])
> LogicalCorrelate(correlation=[$cor0], joinType=[LEFT],
> requiredColumns=[{2}])
> LogicalTableScan(table=[[CATALOG, SALES, EMP]])
> LogicalAggregate(group=[{0, 1}])
> LogicalProject(DEPTNO=[$0], i=[true])
> LogicalProject(DEPTNO=[$0])
> LogicalFilter(condition=[=($cor0.JOB, $1)])
> LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
> {noformat}
> Looking at above it seems RelDecorrelator have some issue where it is coming
> up with Inner Join.
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