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https://issues.apache.org/jira/browse/CALCITE-2393?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16529848#comment-16529848
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Zoltan Haindrich commented on CALCITE-2393:
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there is another way, by looking at the truth table:
| x | x is not null | x <> 5 | (x is not null) and (x <> 5) |
| null | false | *null* | *false* |
| 0 | true | true | true |
| 5 | true | false | false |
x<>5 columns "null" is "false" in case of "unknownAsFalse" is enabled
> RexSimplify optimization error for expression 'x is not null and x <> 5'
> -------------------------------------------------------------------------
>
> Key: CALCITE-2393
> URL: https://issues.apache.org/jira/browse/CALCITE-2393
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.16.0
> Reporter: pengzhiwei
> Assignee: Julian Hyde
> Priority: Major
> Fix For: 1.17.0
>
>
> After the optimization of RexSimplify,the expression 'x is not null and x
> <> 5' (x is nullable) is optimized to 'x<> 5' (RexSimplify#unknownAsFalse is
> true). I think it is not a correct result because when x is null, null<> 5
> should return true,while 'x is not null and x <> 5' return false.
> I think the optimization for "is not null" in
> RexSimplify#simplifyAnd2ForUnknownAsFalse should exclude the case of
> not-equal operator.
> I really confused with this optimization, can you give some
> suggestion,thanks!
>
>
>
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