[ https://issues.apache.org/jira/browse/CALCITE-2936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16799268#comment-16799268 ]
Haisheng Yuan commented on CALCITE-2936: ---------------------------------------- [~danny0405] Let's continue discussion here. I understand that the description in the code concerns you, but I think the comments are misleading, the word should be determine, not estimate. The minRowCount and maxRowCount are provided to help determine whether we can do further optimization, like aggregate / sort removal, existential check, not for cardinality and cost estimation. I don't how much value it will provide if it is an estimate value. Should we update the comments If I don't misunderstand the intention? > Simplify EXISTS or NOT EXISTS sub-query that has "GROUP BY ()" > -------------------------------------------------------------- > > Key: CALCITE-2936 > URL: https://issues.apache.org/jira/browse/CALCITE-2936 > Project: Calcite > Issue Type: New Feature > Reporter: Haisheng Yuan > Priority: Major > Labels: pull-request-available > Time Spent: 1h 20m > Remaining Estimate: 0h > > An EXISTS or NOT EXISTS sub-query whose inner child is an aggregate with no > grouping columns should be simplified to a Boolean constant. > Example: > {code:java} > exists(select sum(i) from X) --> true > not exists(select sum(i) from X) --> false > {code} > 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} -- This message was sent by Atlassian JIRA (v7.6.3#76005)