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Type:
Bug
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Resolution: Fixed
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Priority:
Unknown
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Affects Version/s: None
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Component/s: None
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None
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Not Needed
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Summary
An exception is thrown when performing an aggregate query containing a SortBy(), whose expression is a dictionary entry.
- This query works correctly with the V2 LinqProvider
- The exception is: MongoDB.Driver.Linq.ExpressionNotSupportedException "Expression must be a constant"
- The exception doesn't occur if the dictionary key is hard-coded to a constant value
- Tested with MongoDB.Driver v2.19.0
- I suspect this will also affect array indexes, as well as IndexKeysDefinitions
How to Reproduce
class Translation { public int Id { get; set; } public Dictionary<string, string>? Text { get; set; } } static List<Translation> GetSortedTranslations(IMongoCollection<Translation> collection, string language) { return collection.Aggregate() .SortBy(c => c.Text[language]) // This works in LinqProvider.V2, but not V3 .ToList(); } static List<Translation> GetTranslationsSortedByEnglish(IMongoCollection<Translation> collection) { return collection.Aggregate() .SortBy(c => c.Text["en"]) // This works .ToList(); }
Additional Background
The exception occurs when GetItemMethodToFilterFieldTranslator.TranslateWithStringIndex() calls indexExpression.GetConstantValue<string>(). GetConstantValue expects the expression to be of type ConstantExpression, whereas it is given a MemberAccess of a ConstantExpression. We may want to consider allowing partial execution, eg:
public static TValue GetConstantValue<TValue>(this Expression expression, Expression containingExpression) { if (expression is ConstantExpression constantExpression) { return (TValue)constantExpression.Value; } LambdaExpression lambda = Expression.Lambda(expression); Delegate fn = lambda.Compile(); return (TValue)fn.DynamicInvoke(null); }
- is duplicated by
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- Closed
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- Closed
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- related to
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- Closed
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CSHARP-4574 Check whether we need to call EvaluatePartially in more places in LinqProviderAdapterV3
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- Closed
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