[3.1] Fix to #12729 - Flatten Case expression #20362
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ajcvickers
approved these changes
Mar 23, 2020
Summary of the changes - Added CaseWhenFlatteningExpressionVisitor postprocessor - Recursively collapse relevant CaseExpression
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Description
Customer Impact
Invalid sql generated for query with multi level conditional expression. Some scenarios can work around the problem by rewriting the queries, but when the case statements are generated (e.g. in some OData scenarios) we don't have a good workaround.
How found
Reported by multiple customers.
Test coverage
We have added test to cover this scenario.
Regression?
No.
Risk
Low. Fix is very isolated and the logic the fix employs is straightforward. Quirk added to further mitigate the risk.