Fix incorrect simplification of CASE with constant boolean results #23796
+163
−14
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Expressions such as:
CASE
WHEN <e1> THEN <boolean>
WHEN <e2> THEN <boolean>
...
ELSE <boolean>
END
were being incorrectly optimized. The terms in the rewritten boolean expression
need to reflect the fact that all the preceding conditions should've evaluated
to false in order for a given condition to evaluate to true. The optimization
was ignoring them, which could result in incorrect results when the conditions
are not exclusive.
For example:
CASE
WHEN a OR b THEN false
WHEN a OR c THEN true
END
Previously, it was being rewritten as:
(a OR c) ≡ true
However, if `a` is true, then the first branch of the CASE should be evaluated and
the expression should return false.
losipiuk
approved these changes
Oct 16, 2024
Praveen2112
reviewed
Oct 16, 2024
core/trino-main/src/main/java/io/trino/sql/ir/optimizer/rule/SimplifyRedundantCase.java
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Praveen2112
reviewed
Oct 16, 2024
core/trino-main/src/test/java/io/trino/sql/ir/optimizer/TestSimplifyRedundantCase.java
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Expressions such as:
were being incorrectly optimized. The terms in the rewritten boolean expression need to reflect the fact that all the preceding conditions should've evaluated to false in order for a given condition to evaluate to true. The optimization was ignoring them, which could result in incorrect results when the conditions are not exclusive.
For example:
Previously, it was being rewritten as:
However, if
ais true, then the first branch of the CASE should be evaluated and the expression should return false.Fixes #23787
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