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https://issues.apache.org/jira/browse/CALCITE-2726?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16710396#comment-16710396
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Zoltan Haindrich edited comment on CALCITE-2726 at 12/5/18 5:53 PM:
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Proposed change: invoke simplify directly; without the usage of ExprSimplifier;
because RexSimplifier is able to do the recursion on its own.
* I think this modification also reduces unneccessary re-simplification runs...
* after this change nested things(which are by default not simplified) will not
be simplified (they were earlier).
example: {{$0 + CAST(1 as integer)}} earlier was simplified to {{$0 +
1}}...after this change; things like this will be kept as is.
[~julianhyde] Could you please take a look?
was (Author: kgyrtkirk):
Proposed change: invoked simplify directly; without the usage of ExprSimplifier
as RexSimplifier is able to recurse.
* I think this modification also reduces unneccessary re-simplification runs...
* after this change nested things(which are by default not simplified) will not
be simplified (they were earlier).
example: {{$0 + CAST(1 as integer)}} earlier was simplified to {{$0 +
1}}...after this change; things like this will be kept as is.
> ReduceExpressionRule may oversimplify filter conditions containing nulls
> ------------------------------------------------------------------------
>
> Key: CALCITE-2726
> URL: https://issues.apache.org/jira/browse/CALCITE-2726
> Project: Calcite
> Issue Type: Bug
> Reporter: Zoltan Haindrich
> Assignee: Zoltan Haindrich
> Priority: Major
> Fix For: 1.18.0
>
>
> 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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