核心数据"数据库显示已损坏" - 导致此错误的原因是什么？

Question

我在这里撞墙,我正在使用Core Data作为SQLLite数据库,我能够成功保存到数据库(我已经在离线SQLLite浏览器中检查了内容),但是在保存之后我试图运行的第一个查询返回下面看到的错误,我在互联网上找不到与此特定错误相关的任何有用信息:

核心数据:错误:-executeRequest:遇到异常=数据库显示已损坏.用户信息= {NSFilePath ="/ Users/user/Library/Application Support/iPhone Simulator/7.0.3/Documents/db.sqlite";(无效的主键);

这里的问题是导致这个错误的原因,因为我找不到任何与之相关的信息.

对于一些小背景,这是我的设置,请假设我已经有充分的理由进行设计并且没有提供"改变你的设计"的答案,除非你能看到从根本上打破了模式本身的东西.

我有3个托管对象上下文,它们都是NSPrivateQueueConcurrencyType,第一个(A)附加到持久性存储协调器,第二个(B)有A集作为其父上下文,第三个(C)有B设置为它的父上下文 - 链.原因是C是一个可写上下文,从网络源获取数据并同步并保存它,B是UI元素共享的上下文,我希望它是响应的,最后A是设计的背景上下文卸载任何延迟保存到磁盘关闭上下文B&C

PSC < - A < - B < - C.

如果我取出最后一步(将A保存到PSC),则应用程序运行良好,将所有内容保存在内存中并查询内存中的上下文.崩溃仅在我将保存步骤添加回来后才会发生,并且仅在保存后针对数据库运行的第一个查询运行时发生.我的Save和我的fetch执行都包含在performBlock中:

这是最后一次保存:

- (void)deepSave
{
    // Save to the Save Context which happens in memory, so the actual write to disk operation occurs on background thread
    // Expects to be called with performBlock

    NSError *error = nil;
    [super save:&error];
    NSAssert(!error, error.localizedDescription);

    // Trigger the save context to save to disk, operation will be queued and free up read only context
    NSManagedObjectContext *saveContext = self.parentContext;
    [saveContext performBlock:^{
        NSError *error = nil;
        [saveContext save:&error];
        NSAssert(!error, error.localizedDescription);
    }];
}

这里是执行堆栈(在NSManagedObjectContext Queue线程上)

#0  0x0079588a in objc_exception_throw ()
#1  0x079d98e7 in -[NSSQLiteConnection handleCorruptedDB:] ()
#2  0x078d9b8d in -[NSSQLiteConnection fetchResultSet:usingFetchPlan:] ()
#3  0x078e24a5 in newFetchedRowsForFetchPlan_MT ()
#4  0x078cd48e in -[NSSQLCore newRowsForFetchPlan:] ()
#5  0x078cca8d in -[NSSQLCore objectsForFetchRequest:inContext:] ()
#6  0x078cc53f in -[NSSQLCore executeRequest:withContext:error:] ()
#7  0x078cbf62 in -[NSPersistentStoreCoordinator executeRequest:withContext:error:] ()
#8  0x078c96c6 in -[NSManagedObjectContext executeFetchRequest:error:] ()
#9  0x0791e526 in -[NSManagedObjectContext(_NestedContextSupport) _parentObjectsForFetchRequest:inContext:error:] ()
#10 0x0799c1f4 in __82-[NSManagedObjectContext(_NestedContextSupport) executeRequest:withContext:error:]_block_invoke ()
#11 0x0791e321 in internalBlockToNSManagedObjectContextPerform ()
#12 0x013c34b0 in _dispatch_client_callout ()
#13 0x013b0778 in _dispatch_barrier_sync_f_invoke ()
#14 0x013b0422 in dispatch_barrier_sync_f ()
#15 0x0791e2a2 in _perform ()
#16 0x0791e14e in -[NSManagedObjectContext(_NestedContextSupport) executeRequest:withContext:error:] ()
#17 0x078c96c6 in -[NSManagedObjectContext executeFetchRequest:error:] ()
#18 0x0791e526 in -[NSManagedObjectContext(_NestedContextSupport) _parentObjectsForFetchRequest:inContext:error:] ()
#19 0x0799c1f4 in __82-[NSManagedObjectContext(_NestedContextSupport) executeRequest:withContext:error:]_block_invoke ()
#20 0x0791e321 in internalBlockToNSManagedObjectContextPerform ()
#21 0x013c34b0 in _dispatch_client_callout ()
#22 0x013b0778 in _dispatch_barrier_sync_f_invoke ()
#23 0x013b0422 in dispatch_barrier_sync_f ()
#24 0x0791e2a2 in _perform ()
#25 0x0791e14e in -[NSManagedObjectContext(_NestedContextSupport) executeRequest:withContext:error:] ()
#26 0x078c96c6 in -[NSManagedObjectContext executeFetchRequest:error:] ()

Answer 1

好的,我已经找到了它.对于具有父上下文而不是持久协调器的上下文,在这个设置中,对于NSManagedObject resultType(不应该使用,我们的错误),propertiesToFetch中有一些内容被破坏了.此单元测试显示您所要做的就是设置一个属性来获取以获取此错误(在执行查询时,没有要获取的属性正常工作).我们这里的修复是停止使用属性获取错误:)

- (void)testManagedObjectContextDefect
{        
    NSManagedObjectContext *contextA = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
    contextA.persistentStoreCoordinator = sqllitePersistentStoreCoordinator;
    NSManagedObjectContext *contextB = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
    contextB.parentContext = contextA;

    NSEntityDescription *entityDescription = [NSEntityDescription entityForName:@"GCSCObject" inManagedObjectContext:contextB];

    [contextB performBlockAndWait:^{
        GCSCObject *object = [[GCSCObject alloc] initWithEntity:entityDescription insertIntoManagedObjectContext:contextB];
        object.serverID = @"1";
        NSError *error = nil;
        XCTAssert([contextB save:&error] && !error, @"Failed to save - %@",error); // B -> A save
    }];

    [contextA performBlock:^{
        NSError *error = nil;
        XCTAssert([contextA save:&error] && !error, @"Failed to save - %@",error); // A -> PSC, background save
    }];

    [contextB performBlockAndWait:^{
        NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"GCSCObject"];
        NSError *error = nil;
        NSArray *results = [contextB executeFetchRequest:request error:&error];
        XCTAssert(results.count == 1 && !error, @"Fetch failed to retrieve - %@ / %@",results,error);
        GCSCObject *object = results[0];
        XCTAssert([object.serverID isEqualToString:@"1"], @"Value retrieval failed");

        // Everything passes up to here, so far so good!

        request = [[NSFetchRequest alloc] initWithEntityName:@"GCSCObject"];
        request.propertiesToFetch = @[@"serverID"]; // This is the culprit of the index crash
        results = [contextB executeFetchRequest:request error:&error];
        XCTAssert(!error, @"%@", error.localizedDescription); // !!! HERE we have a failure, assert: "Core Data: error: -executeRequest: encountered exception = The database appears corrupt.  (invalid primary key) with userInfo = { NSFilePath = "/path/db.sqlite }";
    }];
}

在这种情况下,GCSCObject是一个常规实体,serverID是它的参数之一(无论使用哪个参数,或者它是什么类型,我尝试使用多个.这是我用于此的serverID参数的描述测试:

崩溃发生或不发生我们提供和上下文保存(虽然这样做会使得保存后台队列无效)

我喜欢关于为什么会出现这种情况的反馈,但是现在,不使用属性来获取可以让我们的应用程序顺利运行.我正在考虑在这里提交Apple Bug.

Answer 2

如果在执行正在检索某些聚合结果(sum,max,min,...)的获取请求时遇到此错误,请确保设置

fetchRequest.resultType = NSDictionaryResultType;