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Posted to issues@calcite.apache.org by "Laurent Goujon (JIRA)" <ji...@apache.org> on 2018/07/19 22:00:00 UTC
[jira] [Updated] (CALCITE-2421) RexSimplify#simplifyAnds foregoes
some simplications if unknownAsFalse set to true
[ https://issues.apache.org/jira/browse/CALCITE-2421?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Laurent Goujon updated CALCITE-2421:
------------------------------------
Description:
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.
was:
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.
> 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: Julian Hyde
> 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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