Core Data Migration error message "'Model does not contain configuration 'XYZ'.'"

Question

I have a Managed Object Context to which I add two different SQLite stores. I use Configurations in the Mananged Object Model to assign certain entities to one store and other entities to the other. The Configurations are called "UserDB" and "MainDB".

Everything works okay until I try to use automatic migration. After creating a new Managed Object Model version, and adding a new attribute to one of the entities in the UserDB Configuration, I get an exception when adding the old version store (for the UserDB related store) to the store coordinator: 'Model does not contain configuration 'UserDB'.' I can find no hits for this error on Google. Anyone out there using multiple stores with Configurations? Anyone have an idea what I might be doing wrong?

The stack looks like this:

objc_exception_throw
-[NSManagedObjectModel isConfiguration:compatibleWithStoreMetadata:]
-[NSStoreMigrationPolicy sourceModelForStoreAtURL:metadata:error:]
-[NSStoreMigrationPolicy(InternalMethods) _gatherDataAndPerformMigration:]
-[NSPersistentStoreCoordinator addPersistentStoreWithType:configuration:URL:options:error:]
-[MyAppDelegate persistentStoreCoordinator] 

Answer 1

This looks like a bug with migration+configurations. I was able to work around the problem by going through the same motions and passing nil for configuration when calling addPersistentStoreWithType. The migration happens, and then I can make a new persistent store coordinator and add the stores again with the proper Configuration string arguments.

This is the second configuration related bug I've run into. Not a well tested feature apparently.