[jira] [Commented] (CALCITE-1526) Use Strong to infer whether a predicate's inputs may be null

["Jesus Camacho Rodriguez (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-1526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15722119#comment-15722119 ] 

Jesus Camacho Rodriguez commented on CALCITE-1526:
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{{RexUtil.ExprSimplifier}} traverses the expression and simplifies it, choosing whether to recognize UNKNOWN as FALSE depending on 1) the initial value for _ unknownAsFalseCall_, and 2) the expressions found in the traversal.

[~julianhyde], I think it could be extended to use Strong indeed, by checking whether a subexpression might produce UNKNOWN and choosing accordingly the simplify method to call in RexUtil. However, I am still doubting whether that would help to detect further simplification opportunities, or it would just help simplifying/unifying the different code paths.

> Use Strong to infer whether a predicate's inputs may be null
> ------------------------------------------------------------
>
>                 Key: CALCITE-1526
>                 URL: https://issues.apache.org/jira/browse/CALCITE-1526
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Julian Hyde
>            Assignee: Julian Hyde
>
> {{RexImplicationChecker}} must use [Strong|https://calcite.apache.org/apidocs/org/apache/calcite/plan/Strong.html] to infer whether a predicate's inputs may be null. In particular the code in {{RexImplicationChecker.implies2}}.
> Also {{RelMdPredicates.projectPredicate}}.
> [~jcamachorodriguez], Could/should {{RexUtil.ExprSimplifier}} be using {{Strong}}?
> Also, maybe, {{RexUtil.simplifyIs}}.
> Also, {{LogicVisitor}} might be able to deduce that an expression is never null if certain input fields are not null.



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