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https://issues.apache.org/jira/browse/CALCITE-5639?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17711506#comment-17711506
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Julian Hyde commented on CALCITE-5639:
--------------------------------------

It's quite possible that the Javadoc on {{class Strong}} is incorrect. The 
class is rather complicated, especially the reasoning about when an expression 
is "strong on" a particular input argument. That said, I think the 
implementation of the class is strong (pun intended), is well-supported by unit 
tests, and we should use the class more in {{RexSimplify}}.

> RexSimplify should remove IS NOT NULL check when LIKE comparison is present
> ---------------------------------------------------------------------------
>
>                 Key: CALCITE-5639
>                 URL: https://issues.apache.org/jira/browse/CALCITE-5639
>             Project: Calcite
>          Issue Type: Bug
>    Affects Versions: 1.34.0
>            Reporter: Leonid Chistov
>            Assignee: Leonid Chistov
>            Priority: Minor
>              Labels: pull-request-available
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> Consider query like
> {code:java}
> select r_reason_desc from reason
> where r_reason_desc is not null and r_reason_desc like '%child%' 
> {code}
> where "r_reason_desc" is a nullable field.
> When RexSimplify::simplifyFilterPredicates is called on that conjunction of 
> expressions, expression is not simplified, meaning that redundant  "is not 
> null" check is not removed.
> In the same time, if query like 
> {code:java}
> select r_reason_desc from reason
> where r_reason_desc is not null and r_reason_desc >= 'A'{code}
> is passed to optimizer, redundant "is not null" check is eliminated.



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