[CALCITE-1537] Unnecessary project expression in multi-sub-query plan

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.11.0
• Component/s: core
• Labels: sub-query
• Assignee: Julian Hyde
• Reporter: Vineet Garg
• Created: 13/Dec/16 01:18
• Updated: 06/Jan/17 19:30
• Resolved: 27/Dec/16 07:51

Description

Query

 select sal from emp where empno IN (select deptno from dept where emp.job = dept.name)  AND empno IN (select empno from emp e where emp.ename = e.ename) 

Plan just before calling SubqueryRemoveRule

LogicalProject(SAL=[$5])
  LogicalFilter(condition=[AND(IN($0, {
LogicalProject(DEPTNO=[$0])
  LogicalFilter(condition=[=($cor0.JOB, $1)])
    LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
}), IN($0, {
LogicalProject(EMPNO=[$0])
  LogicalFilter(condition=[=($cor0.ENAME, $1)])
    LogicalTableScan(table=[[CATALOG, SALES, EMP]])
}))], variablesSet=[[$cor0]])
    LogicalTableScan(table=[[CATALOG, SALES, EMP]])

Plan just after SubqueryRemoveRule

LogicalProject(SAL=[$5])
  LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
    LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8], DEPTNO0=[$9])
      LogicalJoin(condition=[=($0, $10)], joinType=[inner])
        LogicalFilter(condition=[=($0, $9)])
          LogicalCorrelate(correlation=[$cor0], joinType=[INNER], requiredColumns=[{2}])
            LogicalTableScan(table=[[CATALOG, SALES, EMP]])
            LogicalAggregate(group=[{0}])
              LogicalProject(DEPTNO=[$0])
                LogicalFilter(condition=[=($cor0.JOB, $1)])
                  LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
        LogicalAggregate(group=[{0}])
          LogicalProject(EMPNO=[$0])
            LogicalFilter(condition=[=($cor0.ENAME, $1)])
              LogicalTableScan(table=[[CATALOG, SALES, EMP]])

Plan just after decorrelation

LogicalProject(SAL=[$5], ENAME0=[$9])
  LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8], ENAME0=[$10])
    LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8], DEPTNO0=[$9], ENAME0=[$12])
      LogicalJoin(condition=[=($0, $11)], joinType=[inner])
        LogicalJoin(condition=[AND(=($2, $10), =($0, $9))], joinType=[inner])
          LogicalTableScan(table=[[CATALOG, SALES, EMP]])
          LogicalAggregate(group=[{0, 1}])
            LogicalProject(DEPTNO=[$0], 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]])
        LogicalAggregate(group=[{0, 1}])
          LogicalProject(EMPNO=[$0], ENAME0=[$1])
            LogicalProject(EMPNO=[$0], ENAME0=[$9])
              LogicalJoin(condition=[=($9, $1)], joinType=[inner])
                LogicalTableScan(table=[[CATALOG, SALES, EMP]])
                LogicalAggregate(group=[{0}])
                  LogicalProject(ENAME=[$1])
                    LogicalTableScan(table=[[CATALOG, SALES, EMP]])

As you can notice the top LogicalProject has unnecessary expression ENAME0 after decorrelation

Issue Links

• is depended upon by: CALCITE-1547 Release Calcite 1.11.0
• is related to: CALCITE-1511 Decorrelation fails if query has more than one EXISTS in WHERE clause