[jira] [Created] (HIVE-21010) ReduceExpressionRule may oversimplify filter conditions containing nulls

["Zoltan Haindrich (JIRA)" <ji...@apache.org>]

Zoltan Haindrich created HIVE-21010:
---------------------------------------

             Summary: ReduceExpressionRule may oversimplify filter conditions containing nulls
                 Key: HIVE-21010
                 URL: https://issues.apache.org/jira/browse/HIVE-21010
             Project: Hive
          Issue Type: Bug
            Reporter: Zoltan Haindrich
            Assignee: Zoltan Haindrich



ReduceExpressionsRule is invoking [simplifications|https://github.com/apache/calcite/blob/efec74deb80da1708fd42bcc2b57289840869346/core/src/main/java/org/apache/calcite/rel/rules/ReduceExpressionsRule.java#L549]   - by using [ExprSimplifier|https://github.com/apache/calcite/blob/efec74deb80da1708fd42bcc2b57289840869346/core/src/main/java/org/apache/calcite/rex/RexUtil.java#L2611] which unfortunately doesn't switch unknownAs mode (because it's a visitor).

Can be reproduced by adding the following test case to RelOptRulesTests
{code}
  @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);
  }
{code}

Plan should retain the condition; right now it incorrectly simplified to false.
{code}
    <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>
{code}




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