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SQL: Fix issue with CAST and NULL checking. #50371

Merged
merged 2 commits into from
Dec 19, 2019
Merged

SQL: Fix issue with CAST and NULL checking. #50371

merged 2 commits into from
Dec 19, 2019

Commits on Dec 19, 2019

  1. SQL: Fix issue with CAST and NULL checking. 

    Previously, during expression optimization, CAST would be considered
nullable if the casted expression resulted to a NULL literal, and would
be always non-nullable otherwise. As a result if CASE was wrapped by a
null check function like `IS NULL` or `IS NOT NULL` it was simplified to
TRUE/FALSE, eliminating the actual casting operation. So in case of an
expression with an erroneous casting like `CAST('foo' AS DATETIME) IS NULL`
it would be simplified to `FALSE` instead of throwing an Exception signifying
the attempt to cast 'foo' to a DATETIME type.

CAST now always returns Nullability.UKNOWN except from the case that
its result evaluated to a constant NULL, so it returns Nullability.TRUE.

Fixes: elastic#50191
    @matriv
    matriv committed Dec 19, 2019
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  2. add tests to verify exception

    @matriv
    matriv committed Dec 19, 2019
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