Entity splitting with Complex Property throws InvalidOperationException

[mathiasschaemelhout]

Bug description

When using a Complex Property on an entity that is split across multiple tables using SplitToTable, queries that include the complex property fail with:

System.InvalidOperationException: Sequence contains more than one element

Might be related to #37982, but this example does not use JSON or collections.

Your code

using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;

async Task Main()
{
  await using var context = new TestContext();
  await context.Database.EnsureDeletedAsync();
  await context.Database.EnsureCreatedAsync();

  var hooks = await context.Set<Hook>().ToListAsync();
  Console.WriteLine($"Hooks count: {hooks.Count}");
}

public class TestContext : DbContext
{
  private const string ConnectionString = "Server=localhost,1433;Database=Test;";

  protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder) => optionsBuilder.UseSqlServer(ConnectionString);

  protected override void OnModelCreating(ModelBuilder modelBuilder)
  {
    modelBuilder.Entity<Hook>().HasKey(hook => hook.Id);
    modelBuilder.Entity<Hook>().ComplexProperty(hook => hook.Number); // This seems to be causing the issue

    modelBuilder.Entity<Hook>().SplitToTable(
        "HookMetadata",
        tableBuilder =>
        {
          tableBuilder.Property(hook => hook.Id).HasColumnName("HookId");
          tableBuilder.Property(hook => hook.Weight);
          tableBuilder.Property(hook => hook.IsTestHook);
        });
  }
}

public class Hook
{
  public int Id { get; set; }
  public DateTime CreatedOn { get; set; }
  public HookNumber Number { get; set; }

  // Metadata
  public decimal? Weight { get; set; }
  public bool? IsTestHook { get; set; }
}

public class HookNumber
{
  public string Raw { get; set; }
  public long Parsed { get; set; }
}

Stack traces

System.InvalidOperationException: Sequence contains more than one element
   at System.Linq.ThrowHelper.ThrowMoreThanOneElementException()
   at System.Linq.Enumerable.TryGetSingle[TSource](IEnumerable`1 source, Boolean& found)
   at System.Linq.Enumerable.Single[TSource](IEnumerable`1 source)
   at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.GenerateComplexPropertyShaperExpression(StructuralTypeProjectionExpression containerProjection, IComplexProperty complexProperty)
   at Microsoft.EntityFrameworkCore.Query.StructuralTypeProjectionExpression.BindComplexProperty(IComplexProperty complexProperty)
   at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.<ApplyProjection>g__ProcessType|62_19(StructuralTypeProjectionExpression typeProjection, <>c__DisplayClass62_6&)
   at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.<ApplyProjection>g__AddStructuralTypeProjection|62_0(StructuralTypeProjectionExpression projection)
   at Microsoft.EntityFrameworkCore.Query.SqlExpressions.SelectExpression.ApplyProjection(Expression shaperExpression, ResultCardinality resultCardinality, QuerySplittingBehavior querySplittingBehavior)
   at Microsoft.EntityFrameworkCore.Query.Internal.SelectExpressionProjectionApplyingExpressionVisitor.VisitExtension(Expression extensionExpression)
   at Microsoft.EntityFrameworkCore.Query.RelationalQueryTranslationPostprocessor.Process(Expression query)
   at Microsoft.EntityFrameworkCore.SqlServer.Query.Internal.SqlServerQueryTranslationPostprocessor.Process(Expression query)
   at Microsoft.EntityFrameworkCore.Query.QueryCompilationContext.CreateQueryExecutorExpression[TResult](Expression query)
   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__DisplayClass11_0`1.<ExecuteCore>b__0()
   at Microsoft.EntityFrameworkCore.Query.Internal.CompiledQueryCache.GetOrAddQuery[TResult](Object cacheKey, Func`1 compiler)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteCore[TResult](Expression query, Boolean async, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryCompiler.ExecuteAsync[TResult](Expression query, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryProvider.ExecuteAsync[TResult](Expression expression, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Query.Internal.EntityQueryable`1.GetAsyncEnumerator(CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Internal.InternalDbSet`1.System.Collections.Generic.IAsyncEnumerable<TEntity>.GetAsyncEnumerator(CancellationToken cancellationToken)
   at System.Runtime.CompilerServices.ConfiguredCancelableAsyncEnumerable`1.GetAsyncEnumerator()
   at Microsoft.EntityFrameworkCore.EntityFrameworkQueryableExtensions.ToListAsync[TSource](IQueryable`1 source, CancellationToken cancellationToken)

Verbose output

EF Core version

10.0.5

Database provider

Microsoft.EntityFrameworkCore.SqlServer

Target framework

.NET 10

Operating system

Windows 11

IDE

No response

[roji]

AI Triage

The below is an AI-generated analysis and may contain inaccuracies.

Summary

Confirmed bug. Using ComplexProperty on an entity that uses SplitToTable throws System.InvalidOperationException: Sequence contains more than one element when querying. The crash occurs during projection application in SelectExpression.GenerateComplexPropertyShaperExpression, where a .Single() call encounters multiple likely because entity splitting results in multiple table sources, and the complex property shaper generation doesn't correctly handle this case.elements

Reproduction

Reproduced on SQLite (not provider- the error is in the relational query pipeline).specific

• Confirmed on EF Core 10.0.5 (reported version)
• Confirmed on EF Core 9.x (same stack trace)
  EF 10; the combination of complex properties + entity splitting has likely never worked.

Minimal repro

using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

await using var context = new TestContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

var hooks = await context.Set<Hook>().ToListAsync();
Console.WriteLine($"Hooks count: {hooks.Count}");

public class TestContext : DbContext
{
    public DbSet<Hook> Hooks { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlite("Data Source=test.db")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Hook>().HasKey(hook => hook.Id);
        modelBuilder.Entity<Hook>().ComplexProperty(hook => hook.Number);

        modelBuilder.Entity<Hook>().SplitToTable(
            "HookMetadata",
            tableBuilder =>
            {
                tableBuilder.Property(hook => hook.Id).HasColumnName("HookId");
                tableBuilder.Property(hook => hook.Weight);
                tableBuilder.Property(hook => hook.IsTestHook);
            });
    }
}

public class Hook
{
    public int Id { get; set; }
    public DateTime CreatedOn { get; set; }
    public HookNumber Number { get; set; }
    public decimal? Weight { get; set; }
    public bool? IsTestHook { get; set; }
}

public class HookNumber
{
    public string Raw { get; set; }
    public long Parsed { get; set; }
}

Possible duplicates

• https://github.com/dotnet/efcore/issues/ Very likely the same root cause. That issue reports the same Sequence contains more than one element error with SplitToTable + complex collection (JSON). This issue (Entity splitting with Complex Property throws InvalidOperationException #38077) demonstrates the same crash with a plain (non-JSON, non-collection) complex property + SplitToTable, confirming the bug is broader than just JSON/collections.37982
• https://github.com/dotnet/efcore/issues/ Related but different scenario (TVF/View + complex property, rather than SplitToTable).33129

[roji]

/cc @AndriySvyryd, more entity splitting errors (related to our recent conversation on using the relational model in query).

Putting as a stretch goal for 11.0, though not sure we'll get around to it.

[AndriySvyryd]

Depends on #38060

@roji Btw, the AI triage is not formatting issue links correctly

[roji]

Btw, the AI triage is not formatting issue links correctly

Yeah, though I think it usually does... Let's see if this happens consistently.