ios - 在 CoreData 中设置 NSFetchRequest 的 fetchOffset 结果不一致-6ren

ios - 在 CoreData 中设置 NSFetchRequest 的 fetchOffset 结果不一致

转载作者：可可西里更新时间：2023-11-01 03:55:33

我有下面的方法可以取出一页 CoreData 实体。当我为 start 传递一个值时，我得到了不一致的结果。有时它会像我预期的那样进行分页，有时它真的不会。它似乎从我请求的地方附近的某个地方获得结果，但经常与其他结果交错或跳过一些。

我已经通过在每次请求特定页面时记录所有结果并将结果页面与整个列表进行比较来证明这一点。调试日志如下

关于如何/为什么会发生这种情况有什么想法吗？

+(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;
}

所以运行这个会产生:

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

最佳答案

很难说出您在这里尝试做什么，但这可能是您的错误的来源。

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，将会产生不可预知的结果。 (由于内部优化，一些短字符串实际上会共享相同的内存地址，但大多数字符串将不相等，即使它们包含完全相同的文本)

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，您不是要在这里比较实际的消息对象吗？在这种情况下，您可以使用直接对象比较。

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

关于ios - 在 CoreData 中设置 NSFetchRequest 的 fetchOffset 结果不一致，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/50447862/

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ios - 在 CoreData 中设置 NSFetchRequest 的 fetchOffset 结果不一致