Union of Anonymous Type having hardwired bool property throws exception

[avinash-phaniraj-readify]

Performing a Union of Anonymous Types,
having a hardwired bool property throws exception

[Workaround : making it an expression such as 1 == 1 or even calling an extension method that returns itself gets us around.]

Exception message: An exception occurred while reading a database value. The expected type was 'System.Boolean' but the actual value was of type 'System.Int32'.
Stack trace:
System.InvalidOperationException
  HResult=0x80131509
  Message=An exception occurred while reading a database value. The expected type was 'System.Boolean' but the actual value was of type 'System.Int32'.
  Source=Microsoft.EntityFrameworkCore
  StackTrace:
   at Microsoft.EntityFrameworkCore.Metadata.Internal.EntityMaterializerSource.ThrowReadValueException[TValue](Exception exception, Object value, IPropertyBase property)
   at Microsoft.EntityFrameworkCore.Storage.Internal.TypedRelationalValueBufferFactory.Create(DbDataReader dataReader)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.Enumerator.BufferlessMoveNext(DbContext _, Boolean buffer)
   at Microsoft.EntityFrameworkCore.Storage.Internal.NoopExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
   at Microsoft.EntityFrameworkCore.Query.Internal.QueryingEnumerable`1.Enumerator.MoveNext()
   at System.Linq.Enumerable.<UnionIterator>d__67`1.MoveNext()
   at Microsoft.EntityFrameworkCore.Query.Internal.LinqOperatorProvider.ExceptionInterceptor`1.EnumeratorExceptionInterceptor.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at TestHostForCastException.Program.Main(String[] args) in C:\EFCore\EFCoreTestBed\Program.cs:line 26

Inner Exception 1:
InvalidCastException: Specified cast is not valid.

Steps to reproduce

https://github.com/avinash-phaniraj-readify/EFCoreTestBed.git
Please checkout branch - UnionError

var employees = context.Set<Employee>();
var qualified = employees.Select(s => new { s.Id, IsQualified = true });
var unQualified = employees.Select(s => new { s.Id, IsQualified = false });
qualified.Union(unQualified).ToList();

Further technical details

EF Core version: 2.1.1
Database Provider: EntityFrameworkCore.SqlServerCompact35 2.1.0.1
Operating system: Win 10
IDE: Visual Studio 2017 15.7.2

[divega]

@maumar to check if this is already fixed or something we need to fix.

[maumar]

We have fixed this for sql server in 2.1.3 patch, the issue is tracked here: #12280

@ErikEJ for potential fix in SqlCE. The extensibility point has been added along with the sql server fix - it should just be a matter of implementing ApplyExplicitCastToBoolInProjectionOptimization

[divega]

@maumar can you remind me if this is an issue that may need to be fixed in all providers or is it only in SQL CE?

[ErikEJ]

Also SQL Server it looks like

[maumar]

@divega SqlServer and SqlCE. Sqlite is fine as is, but I'm not sure about postgres.

[roji]

Thanks for thinking about me :)

If I understand this issue correctly, Npgsql/PostgreSQL should be fine because boolean literals are strongly-typed, recognized as such and don't need any casting. Running Correlated_collection_with_complex_order_by_funcletized_to_constant_bool on the current 2.2 branch (where I see the commit has been merged), I get the following SQL on PostgreSQL:

SELECT t.c, t."Nickname", t."SquadId", t."FullName", "g.Weapons"."Name", "g.Weapons"."OwnerFullName"
        FROM "Weapons" AS "g.Weapons"
        INNER JOIN (
            SELECT FALSE AS c, g0."Nickname", g0."SquadId", g0."FullName"
            FROM "Gears" AS g0
            WHERE g0."Discriminator" IN ('Officer', 'Gear')
        ) AS t ON "g.Weapons"."OwnerFullName" = t."FullName"
        ORDER BY t.c DESC NULLS LAST, t."Nickname" NULLS FIRST, t."SquadId" NULLS FIRST, t."FullName" NULLS FIRST

And SELECT FALSE is just fine.

Let me know if you think I need to test or do anything else.