Cosmos: Issues when loading derived type via base set and vice versa

[roji]

See FindCosmosTest.Find_base_type_using_derived_set_tracked (and async), Find_derived_using_base_set_type_from_store (and async).

[smitpatel]

Can you share more details what is the issue?

[roji]

Sure, I didn't dig into it, but as part of #25887 I enabled the FindTestBase suite for Cosmos, and the tests above failed - you can try checking out that PR and remove the skip, and you'll see right away.

[smitpatel]

That is little friction. If you can post exception/error stack trace, generated SQL that would help us evaluate how difficult the fix is.

[roji]

No problem. In Find_derived_using_base_set_type_from_store, Find returns nothing at all, whereas in Find_base_type_using_derived_set_tracked it would seem like we attempt to materialize and track the same instance twice.

Find_base_type_using_derived_set_tracked

System.InvalidOperationException: The instance of entity type 'DerivedType' cannot be tracked because another instance with the key value '{Id: 88}' i...

System.InvalidOperationException
The instance of entity type 'DerivedType' cannot be tracked because another instance with the key value '{Id: 88}' is already being tracked. When attaching existing entities, ensure that only one entity instance with a given key value is attached.
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.ThrowIdentityConflict(InternalEntityEntry entry) in /home/roji/projects/efcore/src/EFCore/ChangeTracking/Internal/IdentityMap.cs:line 253
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.Add(TKey key, InternalEntityEntry entry, Boolean updateDuplicate) in /home/roji/projects/efcore/src/EFCore/ChangeTracking/Internal/IdentityMap.cs:line 279
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.Add(TKey key, InternalEntityEntry entry) in /home/roji/projects/efcore/src/EFCore/ChangeTracking/Internal/IdentityMap.cs:line 231
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.IdentityMap`1.Add(InternalEntityEntry entry) in /home/roji/projects/efcore/src/EFCore/ChangeTracking/Internal/IdentityMap.cs:line 213
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.StartTracking(InternalEntityEntry entry) in /home/roji/projects/efcore/src/EFCore/ChangeTracking/Internal/StateManager.cs:line 566
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState oldState, EntityState newState, Boolean acceptChanges, Boolean modifyProperties) in /home/roji/projects/efcore/src/EFCore/ChangeTracking/Internal/InternalEntityEntry.cs:line 323
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntityEntry.SetEntityState(EntityState entityState, Boolean acceptChanges, Boolean modifyProperties, Nullable`1 forceStateWhenUnknownKey) in /home/roji/projects/efcore/src/EFCore/ChangeTracking/Internal/InternalEntityEntry.cs:line 165
   at Microsoft.EntityFrameworkCore.Cosmos.Query.Internal.CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable`1.TryGenerateIdFromKeys(IProperty idProperty, Object& value) in /home/roji/projects/efcore/src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable.cs:line 163
   at Microsoft.EntityFrameworkCore.Cosmos.Query.Internal.CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable`1.TryGetResourceId(String& resourceId) in /home/roji/projects/efcore/src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable.cs:line 114
   at Microsoft.EntityFrameworkCore.Cosmos.Query.Internal.CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable`1.Enumerator.MoveNext() in /home/roji/projects/efcore/src/EFCore.Cosmos/Query/Internal/CosmosShapedQueryCompilingExpressionVisitor.ReadItemQueryingEnumerable.cs:line 219
   at System.Linq.Enumerable.TryGetSingle[TSource](IEnumerable`1 source, Boolean& found) in System.Linq.dll:token 0x60000f6+0x43
   at lambda_method391(Closure , QueryContext )
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.Execute[TResult](Expression query) in /home/roji/projects/efcore/src/EFCore/Query/Internal/QueryCompiler.cs:line 97
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.Execute[TResult](Expression expression) in /home/roji/projects/efcore/src/EFCore/Query/Internal/EntityQueryProvider.cs:line 78
   at System.Linq.Queryable.FirstOrDefault[TSource](IQueryable`1 source, Expression`1 predicate) in System.Linq.Queryable.dll:token 0x6000132+0x1c
   at Microsoft.EntityFrameworkCore.Internal.EntityFinder`1.Find(Object[] keyValues) in /home/roji/projects/efcore/src/EFCore/Internal/EntityFinder.cs:line 60
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.Find(Object[] keyValues) in /home/roji/projects/efcore/src/EFCore/Internal/InternalDbSet.cs:line 176
   at Microsoft.EntityFrameworkCore.FindCosmosTest.FindCosmosTestSet.Find[TEntity](DbContext context, Object[] keyValues) in /home/roji/projects/efcore/test/EFCore.Cosmos.FunctionalTests/FindCosmosTest.cs:line 40
   at Microsoft.EntityFrameworkCore.FindTestBase`1.Find_base_type_using_derived_set_tracked() in /home/roji/projects/efcore/test/EFCore.Specification.Tests/FindTestBase.cs:line 182

Find_derived_using_base_set_type_from_store

System.NullReferenceException: Object reference not set to an instance of an object.

System.NullReferenceException
Object reference not set to an instance of an object.
   at Microsoft.EntityFrameworkCore.FindTestBase`1.Find_derived_using_base_set_type_from_store() in /home/roji/projects/efcore/test/EFCore.Specification.Tests/FindTestBase.cs:line 207

[ajcvickers]

Investigated this. We have a DbSet<BaseType> and we execute the following query to find a DerivedType with the given key:

DbSet<BaseType>().Where(e => EF.Property<int>(e, "Id") == (int)ValueBuffer.get_Item(0))

For SQL Server with TPH, this translates to the following:

DECLARE @__p_0 int = 78;

SELECT [b].[Id], [b].[Discriminator], [b].[Foo], [b].[Boo]
FROM [BaseType] AS [b]
WHERE [b].[Id] = @__p_0

This finds and returns an instance of the DerivedType, as expected.

For Cosmos, the translation is:

-- @__p_0='78'
SELECT c
FROM root c
WHERE (c["Discriminator"] IN ("BaseType", "DerivedType") AND (c["Id"] = @__p_0))

This does not find the DerivedType instance; it returns no results.

[smitpatel]

That SQL should find derived type instance. It has id value and discriminator for derived type is also included in Where.