[CALCITE-2726] ReduceExpressionRule may oversimplify filter conditions containing nulls

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 1.18.0
• Assignee: Zoltan Haindrich
• Reporter: Zoltan Haindrich
• Created: 05/Dec/18 15:49
• Updated: 23/Dec/18 00:11
• Resolved: 06/Dec/18 08:55

Description

ReduceExpressionsRule is invoking simplifications - by using ExprSimplifier which unfortunately doesn't switch unknownAs mode (because it's a visitor).

Can be reproduced by adding the following test case to RelOptRulesTests

  @Test public void testIncorrectlyRemovedCondition() {
    HepProgram program = new HepProgramBuilder()
        .addRuleInstance(ReduceExpressionsRule.FILTER_INSTANCE)
        .build();

    String sql =
        //        "select * from emp where ( (empno=1 and mgr=1) or (empno=null and mgr=1) ) is null";
        "select * from emp where ( (empno=null and mgr=1) ) is null";
    checkPlanning(program, sql);
  }

Plan should retain the condition; right now it incorrectly simplified to false.

    <TestCase name="testIncorrectlyRemovedCondition">
        <Resource name="sql">
            <![CDATA[select * from emp where ( (empno=null and mgr=1) ) is null]]>
        </Resource>
        <Resource name="planBefore">
            <![CDATA[
LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
  LogicalFilter(condition=[IS NULL(AND(=($0, null), =($3, 1)))])
    LogicalTableScan(table=[[CATALOG, SALES, EMP]])
]]>
        </Resource>
        <Resource name="planAfter">
            <![CDATA[
LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7], SLACKER=[$8])
  LogicalValues(tuples=[[]])
]]>
        </Resource>
    </TestCase>

Issue Links

• links to: PR