Query : SqlServerMathRoundTranslator wrong argument index results in returning incorrect data or throwing InvalidCastException

[rpawlaszek]

Trying to use Math.Round in the query gives InvalidCastException

Exception message: An exception occurred in the database while iterating the results of a query.
Stack trace:
System.InvalidCastException: Specified cast is not valid..
   w lambda_method(Closure , ValueBuffer )
   w System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   w Microsoft.EntityFrameworkCore.Query.Internal.LinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext()

Steps to reproduce

Follow Entity Framework Core docs, build the model, populate Blogs table with few entities and then used this to query:

            using (var db = new BloggingContext())
            {
                LogToConsole(db);
                var query = db.Blogs
                            .Select(b => Math.Round(Math.PI, b.Rating));
                            
                foreach (var item in query)
                {
                    Console.WriteLine($"RESULT is {item}");
                }
            }

The console logging shows what went wrong:

select double Round(
    value: 3,14159265358979,
    digits: b.Rating
)
'
TRACKED: False
(QueryContext queryContext) => IEnumerable<double> _Select(
    source: IEnumerable<ValueBuffer> _ShapedQuery(
        queryContext: queryContext,
        shaperCommandContext: SelectExpression:
            SELECT ROUND([b].[Rating], [b].[Rating])
            FROM [Blogs] AS [b]
        ,
        shaper: ValueBufferShaper
    )
    ,
    selector: (ValueBuffer b) => (double) object b.get_Item(0)
)

The line

SELECT ROUND([b].[Rating], [b].[Rating])

should be

SELECT ROUND(3.14159265358979, [b].[Rating])

and is there because of a bug in SqlServerMathRoundTranslator.cs#L34. There should be

: new[] { methodCallExpression.Arguments[0], methodCallExpression.Arguments[1] })

I did that as I wanted to check whether mathemathical functions are run on the server side. And actually Math.Round wasn't the one I was looking for, but checked them all. I guess I should create another Issue with this, but could you implement trigonometric functions + Math.Sqrt, Math.Log, Math.Log10, Math.Exp as well?

Further technical details

EF Core version: 1.1.0 (but present in all, as I see)
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: Windows 10 Pro
IDE: Visual Studio 2015

[maumar]

Justification for 1.1.1

Impact: Medium. Issue was found by a customer and it may cause incorrect results for simple queries. Severity is mitigated by the fact that scope of the issue is quite narrow (only one method is affected).

Risk: None - fix is one-character change (correcting of a typo), scoped to only one method call (Math.Round)

[Eilon]

This patch bug is approved. Please use the normal code review process w/ a PR and make sure the fix is in the correct branch, then close the bug and mark it as done.

[smitpatel]

✅ Verified