使用Core Data有效显示100,000个项目 [英] efficiently display 100,000 items using Core Data

问题描述

我正在使用NSFetchResultsController在UITableView中显示100,000条以上的记录.可以，但是速度很慢，尤其是在iPad 1上.加载可能需要7秒钟，这对我的用户来说是一种折磨.

I am using a NSFetchResultsController to display 100,000 + records in a UITableView. This works but it is SLOW, especially on an iPad 1. It can take 7 seconds to load which is torture for my users.

我也希望能够使用部分，但这会至少增加3秒钟的工作时间.

I'd also like to be able to use sections but this adds at least another 3 seconds onto the laod time.

这是我的NSFetchResultsController:

Here is my NSFetchResultsController:

- (NSFetchedResultsController *)fetchedResultsController {

    if (self.clientsController != nil) {
        return self.clientsController;
    }

    NSFetchRequest *request = [[NSFetchRequest alloc] init];
    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Client" inManagedObjectContext:self.managedObjectContext];
    [request setEntity:entity];
    [request setPredicate:[NSPredicate predicateWithFormat:@"ManufacturerID==%@", self.manufacturerID]];
    [request setFetchBatchSize:25];

    NSSortDescriptor *sort = [[NSSortDescriptor alloc]  initWithKey:@"UDF1" ascending:YES];
    NSSortDescriptor  *sort2= [[NSSortDescriptor alloc] initWithKey:@"Name" ascending:YES];
    [request setSortDescriptors:[NSArray arrayWithObjects:sort, sort2,nil]];

    NSArray *propertiesToFetch = [[NSArray alloc] initWithObjects:@"Name", @"ManufacturerID",@"CustomerNumber",@"City", @"StateProvince",@"PostalCode",@"UDF1",@"UDF2", nil];
    [request setPropertiesToFetch:propertiesToFetch];

    self.clientsController =
    [[NSFetchedResultsController alloc] initWithFetchRequest:request
                                        managedObjectContext:self.managedObjectContext sectionNameKeyPath:nil
                                                   cacheName:nil];

    return self.clientsController;

}

我在NSPredicate中使用了ManufacturerID的索引.这似乎是一个非常基本的NSFetchRequest-我可以做些什么来加快速度吗?还是我刚刚遇到限制?我一定很想念东西.

I have an index on ManufacturerID which is used in my NSPredicate. This seems like a pretty basic NSFetchRequest - anything I can do to speed this up? Or have I just hit a limitation? I must be missing something.

推荐答案

首先:您可以使用 NSFetchedResultsController 的缓存来加快首次获取后的显示速度.这应该很快下降到几分之一秒.

First: you can use the NSFetchedResultsController's cache to speed up display after the first fetch. This should quickly go down to a fraction of a second.

第二个:您可以尝试仅显示第一个屏幕，然后在后台获取其余屏幕.我通过以下方式执行此操作:

Second: you can try to display the only the first screenful and then fetch the rest in the background. I do this in the following way:

• 当视图出现时，检查您是否具有首页缓存.
• 如果没有，我将获取第一页.您可以通过设置获取请求的 fetchLimit 来完成此操作.
  • 如果您使用的是节，请执行两次快速访存以确定第一个节的标题和记录.
  • 您可以创建一个子上下文并使用 performBlock:或
  • 使用 dispatch_async().

  在我最近的一个项目中，该项目的记录超过200K，效果很好.

  This worked quite well in one of my recent projects with > 200K records.

  这篇关于使用Core Data有效显示100,000个项目的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！