[jira] [Created] (CALCITE-1495) Add a rule to convert INNER JOIN preceded by GROUP BY to appropriate SEMI-JOIN

["Vineet Garg (JIRA)" <ji...@apache.org>]

Vineet Garg created CALCITE-1495:
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             Summary: Add a rule to convert INNER JOIN preceded by GROUP BY to appropriate SEMI-JOIN
                 Key: CALCITE-1495
                 URL: https://issues.apache.org/jira/browse/CALCITE-1495
             Project: Calcite
          Issue Type: New Feature
          Components: core
            Reporter: Vineet Garg
            Assignee: Julian Hyde


For IN and EXISTS subqueries Calcite currently generates plan consisting of GROUP BY on inner table followed by INNER JOIN with outer table.
e.g.  for following query:
{noformat} :select sal from emp where empno IN (select deptno from dept) {noformat}

Generated plan is:
{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=[=($0, $9)], joinType=[inner])
      LogicalTableScan(table=[[CATALOG, SALES, EMP]])
      LogicalAggregate(group=[{0}])
        LogicalProject(DEPTNO=[$0])
          LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
{noformat}

Such cases could be converted using this rule to use SEMI-JOIN to make it more efficient



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