Unable to deduplicate both private and public store

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Created Sep ’23

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I've successfully followed the sample code from Apple: Synchronizing a local store to the cloud to deduplicate entities that are created in the user's private store.

However my app also has a public store that needs deduplication and if I enable the NSPersistentStoreRemoteChangeNotificationPostOptionKey for both the private and public store then no deduplication will occur in my private store.

This is reproducible every time by not setting NSPersistentStoreRemoteChangeNotificationPostOptionKey for the public store.

Has anyone else experienced this and has anyone got a solution to get it to work?

Persistence setup code:

private static func makeStoreDescription(for database: Database) -> NSPersistentStoreDescription {
    let url: URL
    let scope: CKDatabase.Scope
    let configuration: String
    
    switch database {
    case .private:
        url = Self.privateStoreURL
        scope = .private
        configuration = "Private"
    case .public:
        url = Self.publicStoreURL
        scope = .public
        configuration = "Public"
    }
    
    let storeDescription = NSPersistentStoreDescription(url: url)
    storeDescription.cloudKitContainerOptions = .init(containerIdentifier: Config.cloudKitContainerIdentifier)
    storeDescription.cloudKitContainerOptions?.databaseScope = scope
    
    switch database {
    case .private:
        storeDescription.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
        storeDescription.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
    case .public:
        // Uncommented otherwise deduplication doesn't work
        // storeDescription.setOption(true as NSNumber, forKey: NSPersistentHistoryTrackingKey)
        // storeDescription.setOption(true as NSNumber, forKey: NSPersistentStoreRemoteChangeNotificationPostOptionKey)
        break
    }
    
    storeDescription.configuration = configuration
    
    return storeDescription
}

private static func makeContainer(inMemory: Bool = false, useIcloud: Bool) -> NSPersistentCloudKitContainer {
    
    let privateStoreDescription = makeStoreDescription(for: .private)
    let publicStoreDescription = makeStoreDescription(for: .public)
    
    let container = NSPersistentCloudKitContainer(name: "Name", managedObjectModel: managedObjectModel)
    
    container.persistentStoreDescriptions = [privateStoreDescription, publicStoreDescription]
    
    // Don't save information for future use if running in memory...
    if inMemory {
        container.persistentStoreDescriptions.forEach { $0.url = URL(fileURLWithPath: "/dev/null") }
    }
    
    print("useIcloud:", useIcloud)
    
    if !useIcloud {
        container.persistentStoreDescriptions.forEach { $0.cloudKitContainerOptions = nil }
    }
    
    container.loadPersistentStores { storeDescription, error in
        if let error = error as NSError? {
            fatalError("Unresolved error \(error), \(error.userInfo)")
        }
        print("Loaded store configuration:", storeDescription.configuration ?? "")
    }
            
    #if DEBUG
    // Use the container to initialize the development schema.
    // Only necessary whenever changes have been made to the schema.
    //try! container.initializeCloudKitSchema(options: [])
    #endif
    
    container.viewContext.automaticallyMergesChangesFromParent = true
    container.viewContext.mergePolicy = NSMergePolicy.mergeByPropertyObjectTrump
    container.viewContext.transactionAuthor = Self.transactionAuthor
    
    if !inMemory {
        do {
            try container.viewContext.setQueryGenerationFrom(.current)
        } catch {
            fatalError("Failed to pin viewContext to the current generation: \(error)")
        }
    }
    
    return container
}

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