Fix to #29638 - GroupBy generates invalid SQL when using custom database function #30617
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maumar
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Apr 5, 2023
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LGTM, see proposal below about moving the code into TableValuedFunctionExpression.
More generally, it's a bit worrying that forgetting to add cloning logic to a new expression type could cause subtle bugs in this way... Should we think about having this fail-fast if an expression should implement cloning logic but doesn't? I'm not sure exactly which expression types must be cloned; TVFExpression clearly does, is it about TableExpressionBases?
src/EFCore.Relational/Query/SqlExpressions/SelectExpression.Helper.cs
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…ase function Problem is that CloningExpressionVisitor doesn't have proper handling for TableValuedFunctionExpression, and therefore goes through default expression visitor pattern (visit all children, check if there are any changes, if there are return new, if not return the same). Since there are no changes, the same instance is returned from cloning, and causes the problem. Fix is to add proper handling of TVFExpression in the CloningExpressionVisitor so that it produces a proper copy. Also added defensive check that throws if we encounter TableExpressionBase that doesn't implement the cloning logic, so that this never happens again. Fixes #29638
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Problem is that CloningExpressionVisitor doesn't have proper handling for TableValuedFunctionExpression, and therefore goes through default expression visitor pattern (visit all children, check if there are any changes, if there are return new, if not return the same). Since there are no changes, the same instance is returned from cloning, and causes the problem. Fix is to add proper handling of TVFExpression in the CloningExpressionVisitor so that it produces a proper copy.
Fixes #29638