Help Aggregating Data on an IGrouping

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I am having trouble selecting aggregate data after a group by.

For reference, here is SQL that emulates what I am trying to do:

select   
ut.teamid as TeamId, sum(p.value) as Value
from userteams ut
join users u on u.id=ut.UserId
join points p on p.UserId = u.id
group by ut.teamid

Here is my code currently:

var rankedTeamForMonth = query // Query is a query on userteams (same model as from the SQL above)
   .GroupBy(x => x.TeamId)
   .Select(x =>
          new 
           {
                    Value = x.Sum(ut => ut.User.Points.Sum(y => y.Value)),
                    TeamId = x.Key,
           }
   );

I get an error that Query could not be translated

Stack Trace:

   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.<VisitMethodCall>g__CheckTranslated|15_0(ShapedQueryExpression translated, <>c__DisplayClass15_0& )
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryableMethodTranslatingExpressionVisitor.VisitMethodCall(MethodCallExpression methodCallExpression)
   at System.Linq.Expressions.MethodCallExpression.Accept(ExpressionVisitor visitor)
   at System.Linq.Expressions.ExpressionVisitor.Visit(Expression node)
   at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutor[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Storage.Database.CompileQuery[TResult](Expression query, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.CompileQueryCore[TResult](IDatabase database, Expression query, IModel model, Boolean async)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.<>c__DisplayClass9_0`1.<Execute>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetEnumerator()
   at System.Collections.Generic.LargeArrayBuilder`1.AddRange(IEnumerable`1 items)
   at System.Collections.Generic.EnumerableHelpers.ToArray[T](IEnumerable`1 source)
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at System.Linq.SystemCore_EnumerableDebugView`1.get_Items()

EF Core version: 5.0.8 Database provider: Microsoft.EntityFrameworkCore.SqlServer Target framework: .NET 5.0 Operating system: Windows 10 IDE: Rider

[roji]

@jacobhjustice with EF Core 6.0, you can achieve what you want with the following query:

var rankedTeamForMonth = ctx.UserTeams
    .GroupBy(x => x.TeamId)
    .Select(x =>
        new
        {
            Value = x.SelectMany(ut => ut.User.Points).Sum(p => p.Value),
            Id = x.Key,
        });

In other words, instead of a nested Sum within a sum, simply flatten everything first and then perform a single Sum. I’d advise using EF Core 6.0.0 rc1 (which is production-ready version with a go-live license).

[roji]

@jacobhjustice can you please submit a runnable code sample producing the translation exception? It’s difficult to know exactly what you’re doing from a the query fragment above.