[jira] [Commented] (CALCITE-2421) RexSimplify#simplifyAnds foregoes some simplications if unknownAsFalse set to true

["Julian Hyde (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-2421?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16641405#comment-16641405 ] 

Julian Hyde commented on CALCITE-2421:
--------------------------------------

Should be easier to fix now that I've fixed CALCITE-2604.

> RexSimplify#simplifyAnds foregoes some simplications if unknownAsFalse set to true
> ----------------------------------------------------------------------------------
>
>                 Key: CALCITE-2421
>                 URL: https://issues.apache.org/jira/browse/CALCITE-2421
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Laurent Goujon
>            Assignee: Laurent Goujon
>            Priority: Minor
>
> It looks like {{RexSimplify#simplifyAnds}} foregoes some comparison simplifications if {{unknownAsFalse}} is set to true, like {{A = A AND B = B}} which might be simplified to {{A IS NOT NULL AND B IS NOT NULL}} or even {{true}} if {{A}} and {{B}} are known to be not nullable.
> One consequence of this is that the selectivity value might be off as a {{=}} comparison has a selectivity of 15% whereas {{IS NOT NULL}} has a selectivity of 90%.
> The simplication is skipped because {{RexSimplify#simplifyList}} simplify all terms with {{unknownAsFalse}} set to {{false}}, but in {{RexSimplify#simplifyAnd2ForUnknownAsFalse}}, there's no attempt at trying again to simplify each term.



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