NET 5.0 RC1 Table-per-type (TPT): DbUpdateException in SaveChanges when inserting objects with Foreign Key relationship

[tivtag]

Trying out the new Table-per-type (TPT) mapping feature, I get the following DbUpdateException with a FK-Error in SaveChanges, when I:

• create a type hierachy Animal > Pet.
• Pet references PetFood (see property FavouritePetFood).
• Insert both a PetFood and a Pet, that contains the PetFood.

The exception occurs in 5.0.0-rc.1.20451.13 and 6.0.0-alpha.1.20465.1.
All works fine with 5.0.0-preview.8.20407.4!

(Removing the usage of the TPT-Feature, also makes the example work.)

Exception:

Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.
---> Microsoft.Data.SqlClient.SqlException (0x80131904):
Die INSERT-Anweisung steht in Konflikt mit der FOREIGN KEY-Einschränkung \"FK_Pets_PetFoods_FavouritePetFood_Id\". 
Der Konflikt trat in der TestDB_EfBug_FK-Datenbank, Tabelle \"dbo.PetFoods\", column 'PetFoods_Id' auf.
Die Anweisung wurde beendet.
  at Microsoft.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
   at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
  at Microsoft.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady)
   at Microsoft.Data.SqlClient.SqlDataReader.TryConsumeMetaData()
 at Microsoft.Data.SqlClient.SqlDataReader.get_MetaData()
   at Microsoft.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString, Boolean isInternal, Boolean forDescribeParameterEncryption, Boolean shouldCacheForAlwaysEncrypted)
 at Microsoft.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean isAsync, Int32 timeout, Task& task, Boolean asyncWrite, Boolean inRetry, SqlDataReader ds, Boolean describeParameterEncryptionRequest)
   at Microsoft.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, TaskCompletionSource`1 completion, Int32 timeout, Task& task, Boolean& usedCache, Boolean asyncWrite, Boolean inRetry, String method)
  at Microsoft.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
   at Microsoft.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior)
  at Microsoft.Data.SqlClient.SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)\
   at System.Data.Common.DbCommand.ExecuteReader()
   at Microsoft.EntityFrameworkCore.Storage.RelationalCommand.ExecuteReader(RelationalCommandParameterObject parameterObject)
  at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.Execute(IRelationalConnection connection)\r\nClientConnectionId:4d09870f-da62-4915-abea-23a8535e776a\r\nError Number:547,State:0,Class:16
  --- End of inner exception stack trace ---
  at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.Execute(IRelationalConnection connection)
  at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.Execute(IEnumerable`1 commandBatches, IRelationalConnection connection)
  at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChanges(IList`1 entries)
  at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(IList`1 entriesToSave)
  at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(DbContext _, Boolean acceptAllChangesOnSuccess)
  at Microsoft.EntityFrameworkCore.Storage.ExecutionStrategy.ExecuteImplementation[TState,TResult](Func`3 operation, Func`3 verifySucceeded, TState state)
  at Microsoft.EntityFrameworkCore.Storage.ExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
  at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(Boolean acceptAllChangesOnSuccess)
  at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
  at Microsoft.EntityFrameworkCore.DbContext.SaveChanges()\r\n   at EfcBug.Program.Main(String[] _)

Steps to reproduce:

namespace EfcBug
{
    using System;
    using System.ComponentModel.DataAnnotations;
    using System.ComponentModel.DataAnnotations.Schema;
    using Microsoft.EntityFrameworkCore;

    [Table( "Animals" )]
    public class Animal
    {
        [Key]
        [DatabaseGenerated( DatabaseGeneratedOption.Identity )]
        public int Id { get; set; }

        public string Species { get; set; }
    }

    [Table( "Pets" )]
    public class Pet : Animal
    {
        public string Name { get; set; }

        [Column( "FavouritePetFood_Id" )]
        [ForeignKey( nameof( FavouritePetFood ) )]
        public int? FavouritePetFoodId { get; set; }
        public PetFood FavouritePetFood { get; set; }
    }

    [Table( "PetFoods" )]
    public sealed class PetFood
    {
        [Key]
        [DatabaseGenerated( DatabaseGeneratedOption.Identity )]
        [Column( "PetFoods_Id" )]
        public int PetFoodId { get; set; }

        public string FoodName { get; set; }
    }

    public class EfBugDbContext : DbContext
    {
        protected override void OnConfiguring( DbContextOptionsBuilder options )
        {
            options
                .UseSqlServer(
                    "Data Source=localhost;Initial Catalog=TestDB_EfBug_FK;Persist Security Info=True;User ID=User;Password=Pass",
                    providerOptions => providerOptions.EnableRetryOnFailure() )
                .EnableDetailedErrors()
                .EnableSensitiveDataLogging();
        }

        protected override void OnModelCreating( ModelBuilder modelBuilder )
        {
            modelBuilder.Entity<Animal>().ToTable( "Animals" );
            modelBuilder.Entity<Pet>().ToTable( "Pets" ).HasOne( x => x.FavouritePetFood );
            modelBuilder.Entity<PetFood>().ToTable( "PetFoods" );
        }
    }

    public class Program
    {
        static void Main( string[] _ )
        {
            try
            {
                using( EfBugDbContext db = new EfBugDbContext() )
                {
                    db.Database.EnsureCreated();
                }

                using( EfBugDbContext db = new EfBugDbContext() )
                {
                    var petFood = new PetFood() { FoodName = "Fish" };
                    db.Add( petFood );

                    var pet = new Pet() { Name = "Kittykat", FavouritePetFood = petFood };
                    db.Add( pet );

                    db.SaveChanges();
                }

                Console.WriteLine( "OK" );
            }
            catch( Exception ex )
            {
                Console.WriteLine( ex.ToString() );
            }

            Console.ReadLine();
        }
    }
}

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <Configurations>Debug;Release;TestRelease;ReleaseKundeProd;ReleaseKundeTest</Configurations>
  </PropertyGroup>
  
  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <RootNamespace>EfcBug</RootNamespace>
    <AssemblyName>EfcBug</AssemblyName>
  </PropertyGroup>

  <PropertyGroup>
    <PlatformTarget>AnyCPU</PlatformTarget>
    <AutoGenerateBindingRedirects>true</AutoGenerateBindingRedirects>
    <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
    <LangVersion>latest</LangVersion>
    <TreatWarningsAsErrors>false</TreatWarningsAsErrors>
    <Prefer32Bit>false</Prefer32Bit>
    <StartupObject>EfcBug.Program</StartupObject>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="6.0.0-alpha.1.20465.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="6.0.0-alpha.1.20465.1">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.EntityFrameworkCore.Proxies" Version="6.0.0-alpha.1.20465.1" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="6.0.0-alpha.1.20465.1" />
  </ItemGroup>

  <!--<ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="5.0.0-rc.1.20451.13" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="5.0.0-rc.1.20451.13">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.EntityFrameworkCore.Proxies" Version="5.0.0-rc.1.20451.13" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="5.0.0-rc.1.20451.13" />
  </ItemGroup>-->

  <!--<ItemGroup>
    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="5.0.0-preview.8.20407.4" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="5.0.0-preview.8.20407.4">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
      <PrivateAssets>all</PrivateAssets>
    </PackageReference>
    <PackageReference Include="Microsoft.EntityFrameworkCore.Proxies" Version="5.0.0-preview.8.20407.4" />
    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="5.0.0-preview.8.20407.4" />    
  </ItemGroup>-->

</Project>

Further technical details

EF Core version: 5.0.0-rc.1.20451.13 (doesn't work), 6.0.0-alpha.1.20465.1 (doesn't work), 5.0.0-preview.8.20407.4 (works fine!)
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET Core 3.1.8
Operating system: Windows 10 2004
SQL Server 15.0.4063.15
IDE: Visual Studio 2019 16.7.3

[AndriySvyryd]

Looks like the root cause is the same as in #22573

[AndriySvyryd]

There is an additional issue in value propagation