ios – 在CoreData中执行批量INSERT / UPDATE / DELETE的有效方法.

我有一个包含200,000个项目的 JSON对象.我需要迭代这些对象,并确定它们是否存在并执行相关操作(插入/更新/删除).这个shell如下所示.当然,它实际上并没有保存任何东西.更多的是看这种方式需要多长时间.考虑到甚至还没有发生任何变化,这个动作在iPhone 4上处理大约需要8分钟,看起来很疯狂.

有没有更有效的方法来处理这个？

任何建议或指示将不胜感激.

- (void) progressiveInsert
{
    prodAdd = 0;
    prodUpdate = 0;
    prodDelete = 0;

    dispatch_queue_t backgroundDispatchQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0);

    dispatch_async(backgroundDispatchQueue,
                   ^{
                       _productDBCount = 0;

                       NSLog(@"Background Queue");
                       NSLog(@"Number of products in jsonArray: %lu", (unsigned long)[_products count]);

                       NSManagedObjectContext *backgroundThreadContext = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSConfinementConcurrencyType];
                       [backgroundThreadContext setPersistentStoreCoordinator:_persistentStoreCoordinator];
                       [backgroundThreadContext setUndoManager:nil];

                       [fetchRequest setPredicate:predicate];
                       [fetchRequest setEntity:[NSEntityDescription entityForName:@"Products" inManagedObjectContext:_managedObjectContext]];
                       [fetchRequest setIncludesSubentities:NO]; //Omit subentities. Default is YES (i.e. include subentities)
                       [fetchRequest setFetchLimit:1];

                       [_products enumerateObjectsUsingBlock:^(id product, NSUInteger idx, BOOL *stop) {

                           predicate = [NSPredicate predicateWithFormat:@"code == %@", [product valueForKey:@"product_code"]];
                           [fetchRequest setPredicate:predicate];

                           NSError *err;
                           NSArray *fetchedObjects = [_managedObjectContext executeFetchRequest:fetchRequest error:&err];

                           if (fetchedObjects == nil) {

                               if ([[product valueForKey:@"delete"] isEqualToNumber:[NSNumber numberWithBool:TRUE]]){
                                   prodDelete += 1;
                               } else {
                                   prodAdd += 1;
                               }

                           } else {

                               if ([[product valueForKey:@"delete"] isEqualToNumber:[NSNumber numberWithBool:TRUE]]){
                                   prodDelete += 1;
                               } else {
                                   prodUpdate += 1;
                               }

                           }

                           dispatch_sync(dispatch_get_main_queue(), ^
                                         {

                                             self.productDBCount += 1;
                                             float progress = ((float)self.productDBCount / (float)self.totalCount);
                                             _downloadProgress.progress = progress;

                                             if (_productDBCount == _totalCount){
                                                 NSLog(@"Finished processing");
                                                 _endProcessing = [NSDate date];
                                                 [_btn.titleLabel setText:@"Finish"];
                                                 NSLog(@"Processing time: %f", [_endProcessing timeIntervalSinceDate:_startProcessing]);
                                                 NSLog(@"Update: %i // Add: %i // Delete: %i", prodUpdate, prodAdd, prodDelete);
                                                 [self completeUpdateProcess];

                                             }

                                         });


                       }];


                   });
}

看一下
Implementing Find-or-Create Efficiently在“核心数据编程指南”中.

(更新：当前的核心数据编程指南中不再存在本章.可以在以下位置找到存档版本
http://web.archive.org/web/20150908024050/https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreData/Articles/cdImporting.html.)

其中一个关键想法是不对每个产品执行一次获取请求,而是执行一个
带有谓词的“批量提取”

[NSPredicate predicateWithFormat:@"code IN %@", productCodes]

其中productCodes是来自JSON数据的“许多”产品代码数组.当然,您必须找到最佳的“批量大小”.