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https://issues.apache.org/jira/browse/CALCITE-4446?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Julian Hyde updated CALCITE-4446:
---------------------------------
Description:
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:
* {{Sarg(10, 20, UNKNOWN AS TRUE)}}: {{x IS NULL OR x IN (10, 20)}} → TRUE
* {{Sarg(10, 20, UNKNOWN AS UNKNOWN)}}: {{x IN (10, 20)}} → UNKNOWN
* {{Sarg(10, 20, UNKNOWN AS FALSE)}}: {{x IS NOT NULL AND (x IN (10, 20))}}
→ 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.
was:
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)}} →
TRUE
* {{SEARCH(10, 20, UNKNOWN AS UNKNOWN)}}: {{x IN (10, 20)}} → UNKNOWN
* {{SEARCH(10, 20, UNKNOWN AS FALSE)}}: {{x IS NOT NULL AND (x IN (10, 20))}}
→ 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.
> 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
> Priority: Major
>
> 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:
> * {{Sarg(10, 20, UNKNOWN AS TRUE)}}: {{x IS NULL OR x IN (10, 20)}} →
> TRUE
> * {{Sarg(10, 20, UNKNOWN AS UNKNOWN)}}: {{x IN (10, 20)}} → UNKNOWN
> * {{Sarg(10, 20, UNKNOWN AS FALSE)}}: {{x IS NOT NULL AND (x IN (10, 20))}}
> → 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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