Troubles with Grouping

Hi. The following query is resulting in an InvalidCastException and I am not sure why.

from stat in ProductStats
join cart in ShoppingCarts on stat.ShoppingCartId equals cart.Id
group stat by new { cart.CreatedOn.Date, stat.ProductId } into g 
select g

Stack trace

at System.Int32.System.IConvertible.ToDateTime(IFormatProvider provider)
at System.Convert.ChangeType(Object value, Type conversionType, IFormatProvider provider)
at Mindscape.LightSpeed.Linq.Utils.TypeHelper.NonNullableConvert(Object value, Type targetType)
at Mindscape.LightSpeed.Linq.Utils.TypeHelper.NullableSafeConvert(Object value, Type targetType)
at Mindscape.LightSpeed.Linq.Plan.GroupResultsPlan.ExecuteImmediate(IUnitOfWork unitOfWork, Type returnType)
at Mindscape.LightSpeed.Linq.LinqQueryProvider.Execute(Expression expression)
at Mindscape.LightSpeed.Linq.LinqQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression)
at Mindscape.LightSpeed.Linq.LinqQuery`1.System.Collections.IEnumerable.GetEnumerator()

I can rewrite the query as

from stat in ProductStats
group stat by new { stat.ShoppingCart.CreatedOn.Date, stat.ProductId } into g 
select g

but this results in a NullReferenceException StackTrace

at ..€(SelectStatement , Group )
at ..€(AliasedTypeModel , QueryExpression , Order , Group , String , Boolean , Boolean )
at ..€(LightSpeedContext , List`1 , QueryExpression , Order , Group , String , Boolean , Boolean )
at ..€(List`1 , Query , String , IdentifierExpression )
at ..€(Query )
at Mindscape.LightSpeed.UnitOfWork.Project(Query query)
at Mindscape.LightSpeed.Linq.Plan.GroupResultsPlan.ExecuteImmediate(IUnitOfWork unitOfWork, Type returnType)
at Mindscape.LightSpeed.Linq.LinqQueryProvider.Execute(Expression expression)
at Mindscape.LightSpeed.Linq.LinqQueryProvider.System.Linq.IQueryProvider.Execute(Expression expression)
at Mindscape.LightSpeed.Linq.LinqQuery`1.System.Collections.IEnumerable.GetEnumerator() 

Any thoughts as to what could be wrong?

Cheers.

Apparently if I materialise the first table, the join table is materialised with it and I get a result I can live with

from stat in ProductStats.ToList()
join cart in ShoppingCarts on stat.ShoppingCartId equals cart.Id
group stat by new { cart.CreatedOn.Date, stat.ProductId } into g 
select g

(although materialising both tables is obviously not the best solution!)

Hi Andy,

The original issue is hitting a limitation with our support with the use of functions as grouping keys - there has been a backlog item to work on this so I will progress this and get this added in to the nightly build for you soon which will sort this out.

The second issue (the rewritten query which had the NullReferenceException) behaves a bit different for me in a repro case here but ultimately its falling over because we dont support the use of traversals in grouping keys (in this case you are ShoppingCart.CreatedOn with the function for the .Date member wrapped around it). Ill have a look if I can sort this out at the same time as covering off the original issue as well.

I will post an update once I have some progress here which should be within the next day or two and all going well I should an update in the nightly builds for you soon.

Jeremy

Hi Andy,

We had added these two changes into the nightly builds now, let us know how you get on.

Jeremy