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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