Query: optimize CASE statement - remove conditions that are never hit

[maumar]

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CASE
        WHEN CAST(0 AS bit) THEN x
        ELSE y
    END

we can simply remove the WHEN block since it's condition is never met so the result would be just y

If all the WHEN blocks have been removed and there is no ELSE condition we can return NULL

[smitpatel]

@maumar - Is this already done?

[ranma42]

Yes, this should already be optimized by https://github.com/dotnet/efcore/blob/ecd6104d7db803a976116a49d5855bce85634051/src/EFCore.Relational/Query/SqlNullabilityProcessor.cs#L525-L532

EDIT: clauses whose test is NULL instead of FALSE are currently left in; I'm working on it.