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

["Laurent Goujon (JIRA)" <ji...@apache.org>]

Laurent Goujon created CALCITE-2421:
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             Summary: 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


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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