[jira] [Created] (CALCITE-2936) Existential subquery that has aggregate without grouping key should be simplified

["Haisheng Yuan (JIRA)" <ji...@apache.org>]

Haisheng Yuan created CALCITE-2936:
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             Summary: Existential subquery that has aggregate without grouping key should be simplified
                 Key: CALCITE-2936
                 URL: https://issues.apache.org/jira/browse/CALCITE-2936
             Project: Calcite
          Issue Type: New Feature
            Reporter: Haisheng Yuan


An existential subquery whose inner child is an aggregate with no grouping columns should be simplified to a Boolean constant.

Example:
exists(select sum(i) from X) --> true
not exists(select sum(i) from X) --> false

Repro:
{code:java}
@Test public void testExistentialSubquery() {
    final String sql = "SELECT e1.empno\n"
        + "FROM emp e1 where exists\n"
        + "(select avg(sal) from emp e2 where e1.empno = e2.empno )";
    sql(sql).decorrelate(true).ok();
  }
{code}

We got plan:
{code:java}
LogicalProject(EMPNO=[$0])
  LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8], EMPNO0=[CAST($9):INTEGER], $f1=[CAST($10):BOOLEAN])
    LogicalJoin(condition=[=($0, $9)], joinType=[inner])
      LogicalTableScan(table=[[CATALOG, SALES, EMP]])
      LogicalAggregate(group=[{0}], agg#0=[MIN($1)])
        LogicalProject(EMPNO=[$0], $f0=[true])
          LogicalAggregate(group=[{0}], EXPR$0=[AVG($1)])
            LogicalProject(EMPNO=[$0], SAL=[$5])
              LogicalTableScan(table=[[CATALOG, SALES, EMP]])
{code}

The preferred plan should be:

{code:java}
LogicalProject(EMPNO=[$0])
  LogicalTableScan(table=[[CATALOG, SALES, EMP]])
{code}




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