在CoreData中设置NSFetchRequest的fetchOffset导致结果不一致

Question

我有下面的方法，它获取一个CoreData实体的页面。当我传入start的值时，我得到的结果不一致。有时候它会像我期望的那样翻页，有时它确实没有。它似乎从我请求的地方附近获得结果，但经常与其他结果交错或跳过一些结果。

我通过在请求特定页面并将结果页面与整个列表进行比较时记录所有结果来证明这一点。调试日志

有关如何/为何如此发生的任何想法？

+(NSArray *)fetchMessagesForUser:(int32_t)userId connectionUserId:(int32_t)connectionUserId sortASC:(BOOL)sortASC startAt:(int)start size:(int)size sinceMessage:(ChatMessage*)since
{
    NSManagedObjectContext *context = [RKManagedObjectStore defaultStore].mainQueueManagedObjectContext;
    NSFetchRequest *fetchRequest = [ChatMessage fetchRequest];
    NSString *query = @"";
    query = [NSString stringWithFormat:@"(receiverId == %1$d && senderId == %2$d ) || (receiverId == %2$d  && senderId == %1$d) ",userId, connectionUserId];

    NSPredicate *predicate = [NSPredicate predicateWithFormat:query];
    fetchRequest.predicate = predicate;

    NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"dateSent" ascending:sortASC];
    [fetchRequest setSortDescriptors:@[sort]];

    if (size > 0) {
      fetchRequest.fetchLimit = size;
    }
    if (start > 0) {
      fetchRequest.fetchOffset = start;
    }
    NSError *error = nil;
    NSArray *messages = [context executeFetchRequest:fetchRequest error:&error];

    if (start > 0) {
      fetchRequest.fetchLimit = 0;
      fetchRequest.fetchOffset = 0;
      NSArray *allMessages = [context executeFetchRequest:fetchRequest error:&error];
      for (int i = 0; i < allMessages.count; i++) {
         bool inPaged = NO;
         for (int j = 0; j < messages.count; j++) {
            if ([allMessages[i] text] == [messages[j] text]) {
               inPaged = YES;
            }
         }
         NSLog(@"DEBUG fetchOffset: %@: %d", inPaged ? @"SAME" : @"DIFF", [allMessages[i] id]);
      }
      NSLog(@"DEBUG fetchOffset: Finished iterating and comparing the paged vs full result set");
    }

    //Remove non-unique messages (uniqueness determined by ID)
    NSMutableArray* originalMessages = [NSMutableArray arrayWithArray:messages];
    NSMutableArray* filteredMessages = [NSMutableArray array];
    for (int i = 0; i < [originalMessages count]; i++) {
        for (int j = 0; j < [originalMessages count]; j++) {
            if (i != j && [[originalMessages objectAtIndex:i] text] == [[originalMessages objectAtIndex:j] text]) {
                [context deleteObject:[originalMessages objectAtIndex:j]];
                [originalMessages removeObject:[originalMessages objectAtIndex:j]];
            }
        }
        [filteredMessages addObject:[originalMessages objectAtIndex:i]];
    }
    return filteredMessages;
}

所以运行它会产生：

2018-05-21 12:15:40.800686+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22506
2018-05-21 12:15:40.800860+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22505
2018-05-21 12:15:40.801002+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22500
2018-05-21 12:15:40.801168+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22499
2018-05-21 12:15:40.801335+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22498
2018-05-21 12:15:40.801473+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22497
2018-05-21 12:15:40.801606+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22496
2018-05-21 12:15:40.801756+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22495
2018-05-21 12:15:40.801852+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22494
2018-05-21 12:15:40.801965+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22491
2018-05-21 12:15:40.802108+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22490
2018-05-21 12:15:40.802228+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22489
2018-05-21 12:15:40.802370+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22488
2018-05-21 12:15:40.802583+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22487
2018-05-21 12:15:40.802838+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22486
2018-05-21 12:15:40.803034+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22485
2018-05-21 12:15:40.803251+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22484
2018-05-21 12:15:40.803479+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22483
2018-05-21 12:15:40.803723+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22478
2018-05-21 12:15:40.803946+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 SAME: 22477
2018-05-21 12:15:40.804228+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22476
2018-05-21 12:15:40.804399+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22475
2018-05-21 12:15:40.804631+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22474
2018-05-21 12:15:40.804849+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22473
2018-05-21 12:15:40.805158+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22472
2018-05-21 12:15:40.805362+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22469
2018-05-21 12:15:40.805585+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22464
2018-05-21 12:15:40.805766+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22463
2018-05-21 12:15:40.805984+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22462
2018-05-21 12:15:40.806185+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22461
2018-05-21 12:15:40.806385+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22460
2018-05-21 12:15:40.806595+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22459
2018-05-21 12:15:40.806843+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22458
2018-05-21 12:15:40.807031+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22457
2018-05-21 12:15:40.807265+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22456
2018-05-21 12:15:40.807453+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22455
2018-05-21 12:15:40.807649+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22454
2018-05-21 12:15:40.807862+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22453
2018-05-21 12:15:40.808007+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22450
2018-05-21 12:15:40.808216+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22449
2018-05-21 12:15:40.808430+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22445
2018-05-21 12:15:40.808607+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22444
2018-05-21 12:15:40.808775+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22441
2018-05-21 12:15:40.808897+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22438
2018-05-21 12:15:40.809049+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22437
2018-05-21 12:15:40.809209+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22434
2018-05-21 12:15:40.809352+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22433
2018-05-21 12:15:40.809507+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22432
2018-05-21 12:15:40.809688+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22429
2018-05-21 12:15:40.809848+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22428
2018-05-21 12:15:40.814283+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22427
2018-05-21 12:15:40.814416+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22426
2018-05-21 12:15:40.814593+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22425
2018-05-21 12:15:40.814727+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22424
2018-05-21 12:15:40.814849+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22423
2018-05-21 12:15:40.815018+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22421
2018-05-21 12:15:40.815161+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22417
2018-05-21 12:15:40.815276+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22416
2018-05-21 12:15:40.815384+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22415
2018-05-21 12:15:40.815492+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22414
2018-05-21 12:15:40.815617+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22413
2018-05-21 12:15:40.815749+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22412
2018-05-21 12:15:40.815872+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22411
2018-05-21 12:15:40.815965+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22410
2018-05-21 12:15:40.816085+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22409
2018-05-21 12:15:40.816180+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22408
2018-05-21 12:15:40.816302+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22407
2018-05-21 12:15:40.817152+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 10 DIFF: 22406
2018-05-21 12:15:40.817326+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: Finished iterating and comparing the paged vs full result set
2018-05-21 12:16:54.251517+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22506
2018-05-21 12:16:54.251660+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22505
2018-05-21 12:16:54.251820+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22500
2018-05-21 12:16:54.251937+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22499
2018-05-21 12:16:54.252047+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22498
2018-05-21 12:16:54.252166+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22497
2018-05-21 12:16:54.252284+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22496
2018-05-21 12:16:54.252408+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22495
2018-05-21 12:16:54.252526+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22494
2018-05-21 12:16:54.252609+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22491
2018-05-21 12:16:54.252754+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22490
2018-05-21 12:16:54.252885+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22489
2018-05-21 12:16:54.252988+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22488
2018-05-21 12:16:54.253109+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22487
2018-05-21 12:16:54.253230+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22486
2018-05-21 12:16:54.253378+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22485
2018-05-21 12:16:54.253634+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22484
2018-05-21 12:16:54.253874+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22483
2018-05-21 12:16:54.254051+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22478
2018-05-21 12:16:54.254318+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 SAME: 22477
2018-05-21 12:16:54.254489+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22476
2018-05-21 12:16:54.254741+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22475
2018-05-21 12:16:54.254923+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22474
2018-05-21 12:16:54.255103+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22473
2018-05-21 12:16:54.255327+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22472
2018-05-21 12:16:54.255549+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22469
2018-05-21 12:16:54.255712+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22464
2018-05-21 12:16:54.255868+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22463
2018-05-21 12:16:54.256065+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22462
2018-05-21 12:16:54.256349+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22461
2018-05-21 12:16:54.256567+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22460
2018-05-21 12:16:54.256784+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22459
2018-05-21 12:16:54.257163+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22458
2018-05-21 12:16:54.257400+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22457
2018-05-21 12:16:54.257617+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22456
2018-05-21 12:16:54.257823+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22455
2018-05-21 12:16:54.258047+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22454
2018-05-21 12:16:54.258252+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22453
2018-05-21 12:16:54.258495+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22450
2018-05-21 12:16:54.258760+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22449
2018-05-21 12:16:54.259016+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22445
2018-05-21 12:16:54.259250+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22444
2018-05-21 12:16:54.259426+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22441
2018-05-21 12:16:54.259666+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22438
2018-05-21 12:16:54.259869+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22437
2018-05-21 12:16:54.260084+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22434
2018-05-21 12:16:54.260284+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22433
2018-05-21 12:16:54.260463+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22432
2018-05-21 12:16:54.260689+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22429
2018-05-21 12:16:54.260869+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22428
2018-05-21 12:16:54.261060+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22427
2018-05-21 12:16:54.261249+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22426
2018-05-21 12:16:54.261393+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22425
2018-05-21 12:16:54.261519+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22424
2018-05-21 12:16:54.261726+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22423
2018-05-21 12:16:54.261895+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22421
2018-05-21 12:16:54.262061+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22417
2018-05-21 12:16:54.266362+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22416
2018-05-21 12:16:54.266543+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22415
2018-05-21 12:16:54.266730+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22414
2018-05-21 12:16:54.266901+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22413
2018-05-21 12:16:54.267026+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22412
2018-05-21 12:16:54.267106+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22411
2018-05-21 12:16:54.267186+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22410
2018-05-21 12:16:54.267290+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22409
2018-05-21 12:16:54.267474+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22408
2018-05-21 12:16:54.267586+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22407
2018-05-21 12:16:54.267702+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 19 DIFF: 22406
2018-05-21 12:16:54.267809+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: Finished iterating and comparing the paged vs full result set
2018-05-21 12:19:17.342345+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22506
2018-05-21 12:19:17.342518+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22505
2018-05-21 12:19:17.342665+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22500
2018-05-21 12:19:17.342818+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22499
2018-05-21 12:19:17.342937+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22498
2018-05-21 12:19:17.343049+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22497
2018-05-21 12:19:17.343142+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22496
2018-05-21 12:19:17.343269+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22495
2018-05-21 12:19:17.343406+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22494
2018-05-21 12:19:17.343713+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22491
2018-05-21 12:19:17.344044+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22490
2018-05-21 12:19:17.344176+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22489
2018-05-21 12:19:17.344372+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22488
2018-05-21 12:19:17.344696+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22487
2018-05-21 12:19:17.344853+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22486
2018-05-21 12:19:17.345044+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22485
2018-05-21 12:19:17.345220+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22484
2018-05-21 12:19:17.345566+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22483
2018-05-21 12:19:17.345811+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22478
2018-05-21 12:19:17.346076+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22477
2018-05-21 12:19:17.346296+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22476
2018-05-21 12:19:17.346558+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22475
2018-05-21 12:19:17.346758+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22474
2018-05-21 12:19:17.347009+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22473
2018-05-21 12:19:17.347284+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22472
2018-05-21 12:19:17.347519+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22469
2018-05-21 12:19:17.347769+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22464
2018-05-21 12:19:17.348020+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22463
2018-05-21 12:19:17.348312+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22462
2018-05-21 12:19:17.348582+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 SAME: 22461
2018-05-21 12:19:17.348887+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22460
2018-05-21 12:19:17.349143+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22459
2018-05-21 12:19:17.349351+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22458
2018-05-21 12:19:17.349544+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22457
2018-05-21 12:19:17.349903+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22456
2018-05-21 12:19:17.350105+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22455
2018-05-21 12:19:17.350390+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22454
2018-05-21 12:19:17.350681+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22453
2018-05-21 12:19:17.350914+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22450
2018-05-21 12:19:17.351102+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22449
2018-05-21 12:19:17.351314+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22445
2018-05-21 12:19:17.351539+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22444
2018-05-21 12:19:17.351829+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22441
2018-05-21 12:19:17.352039+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22438
2018-05-21 12:19:17.352298+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22437
2018-05-21 12:19:17.352536+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22434
2018-05-21 12:19:17.352891+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22433
2018-05-21 12:19:17.353091+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22432
2018-05-21 12:19:17.353326+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22429
2018-05-21 12:19:17.353538+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22428
2018-05-21 12:19:17.353866+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22427
2018-05-21 12:19:17.354123+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22426
2018-05-21 12:19:17.354437+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22425
2018-05-21 12:19:17.354662+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22424
2018-05-21 12:19:17.354830+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22423
2018-05-21 12:19:17.355050+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22421
2018-05-21 12:19:17.355259+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22417
2018-05-21 12:19:17.355454+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22416
2018-05-21 12:19:17.355644+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22415
2018-05-21 12:19:17.355881+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22414
2018-05-21 12:19:17.356109+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22413
2018-05-21 12:19:17.356387+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22412
2018-05-21 12:19:17.356555+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22411
2018-05-21 12:19:17.356742+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22410
2018-05-21 12:19:17.356931+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22409
2018-05-21 12:19:17.357140+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22408
2018-05-21 12:19:17.357365+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22407
2018-05-21 12:19:17.357543+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: 20 DIFF: 22406
2018-05-21 12:19:17.357734+0100 Link-ages Hub[68958:9889355] DEBUG fetchOffset: Finished iterating and comparing the paged vs full result set

Answer 1

很难说出你要在这里做什么，但这可能是你的错误来源。

if ([allMessages[i] text] == [messages[j] text]) {

这不是字符串比较，因此如果您使用它来比较字符串，它将具有不可预测的结果。 （由于内部优化，一些短字符串实际上将共享相同的内存地址，但大多数字符串即使包含完全相同的文本也不会相等）

您应该使用isEqualToString:来比较字符串。

if ([[allMessages[i] text] isEqualToString:[messages[j] text]]) {

-

然而，即使这可能不是您在调试测试中想要的，您是不是想在这里比较实际的消息对象？在这种情况下，您可以使用直接对象比较。

if (allMessages[i] == messages[j]) {