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Posted to issues@calcite.apache.org by "Julian Hyde (Jira)" <ji...@apache.org> on 2020/12/23 21:28:00 UTC

[jira] [Created] (CALCITE-4446) Implement three-valued logic for SEARCH operator

Julian Hyde created CALCITE-4446:
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             Summary: Implement three-valued logic for SEARCH operator 
                 Key: CALCITE-4446
                 URL: https://issues.apache.org/jira/browse/CALCITE-4446
             Project: Calcite
          Issue Type: Bug
            Reporter: Julian Hyde


Implement three-valued logic for SEARCH operator.

Consider the expression {{x IN (10, 20)}}, which we might represent as {{SEARCH(x, SARG(10, 20))}}. Suppose we invoke this with a value of {{NULL}} for {{x}}. Do we want it to return UNKNOWN, FALSE or TRUE? The answer is: all of the above.

Here are the 3 variants:
* {{SEARCH(10, 20, UNKNOWN AS TRUE)}}: {{x IS NULL OR x IN (10, 20)}} &rarr; TRUE
* {{SEARCH(10, 20, UNKNOWN AS UNKNOWN)}}: {{x IN (10, 20)}} &rarr; UNKNOWN
* {{SEARCH(10, 20, UNKNOWN AS FALSE)}}: {{x IS NOT NULL AND (x IN (10, 20))}} &rarr; FALSE

Currently {{class Sarg}} has a field {{boolean containsNull}} which deals with the first two cases. Changing {{boolean containsNull}} to {{RexUnknownAs unknownAs}} (which has 3 values) will allow us to represent the third. The new representation is symmetrical under negation, which de Morgan's law suggests is a good thing.



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