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我在数据库中只有 3237 条记录，我使用 UISearchDisplayController 和 NSFetchedResultsController 进行搜索。但是当我输入关键字进行搜索时，速度非常慢：

2012-06-26 10:26:25.264 KYBD[3863:707] CoreData: sql: SELECT 0, t0.Z_PK, t0.Z_OPT, t0.ZARTICLEPARTCHINESE, t0.ZARTICLEPARTENGLISH, t0.ZARTICLEPARTNUMBER, t0.ZARTICLE FROM ZARTICLECONTENT t0 LEFT OUTER JOIN ZARTICLES t1 ON t0.ZARTICLE = t1.Z_PK WHERE ( NSCoreDataStringSearch( t0.ZARTICLEPARTENGLISH, ?, 257, 0) OR  NSCoreDataStringSearch( t0.ZARTICLEPARTCHINESE, ?, 257, 0)) ORDER BY t1.ZARTICLETITLE, t0.ZARTICLEPARTNUMBER
2012-06-26 10:26:26.438 KYBD[3863:707] CoreData: annotation: sql connection fetch time: 0.5325s
2012-06-26 10:26:26.446 KYBD[3863:707] CoreData: annotation: total fetch execution time: 1.1821s for 2549 rows.
2012-06-26 10:26:26.489 KYBD[3863:707] CoreData: sql: SELECT  t1.ZARTICLETITLE, COUNT (DISTINCT  t0.Z_PK) FROM ZARTICLECONTENT t0 LEFT OUTER JOIN ZARTICLES t1 ON t0.ZARTICLE = t1.Z_PK WHERE ( NSCoreDataStringSearch( t0.ZARTICLEPARTENGLISH, ?, 257, 0) OR  NSCoreDataStringSearch( t0.ZARTICLEPARTCHINESE, ?, 257, 0)) GROUP BY  t1.ZARTICLETITLE ORDER BY t1.ZARTICLETITLE
2012-06-26 10:26:26.874 KYBD[3863:707] CoreData: annotation: sql connection fetch time: 0.3733s
2012-06-26 10:26:26.879 KYBD[3863:707] CoreData: annotation: total fetch execution time: 0.3904s for 100 rows.

我的 NSFetchedResultsController 代码：

- (NSFetchedResultsController *)fetchedResultsController {
    if (!_fetchedResultsController) {
        NSFetchRequest *request = [[NSFetchRequest alloc] init];
        request.entity = [NSEntityDescription entityForName:@"ArticleContent" inManagedObjectContext:self.managedObjectContext];
        NSSortDescriptor *sort = [NSSortDescriptor sortDescriptorWithKey:@"article.articleTitle" ascending:YES];
        NSSortDescriptor *sort2 = [NSSortDescriptor sortDescriptorWithKey:@"articlePartNumber" ascending:YES];
        request.sortDescriptors = [NSArray arrayWithObjects:sort, sort2, nil];
        request.predicate = nil;

        [NSFetchedResultsController deleteCacheWithName:@"searchResults"];
        _fetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:request managedObjectContext:self.managedObjectContext sectionNameKeyPath:@"article.articleTitle" cacheName:@"searchResults"];
    }

    return _fetchedResultsController;
}

和搜索代码：

- (BOOL)searchDisplayController:(UISearchDisplayController *)controller shouldReloadTableForSearchString:(NSString *)searchString {
    if ([searchString length] > 0) {
        [NSObject cancelPreviousPerformRequestsWithTarget:self.fetchedResultsController selector:@selector(performFetch:) object:nil];
        NSPredicate *predicate = [NSPredicate predicateWithFormat:@"articlePartEnglish CONTAINS[c] %@ OR articlePartChinese CONTAINS[c] %@", searchString, searchString];
        self.fetchedResultsController.fetchRequest.predicate = predicate;
        [NSFetchedResultsController deleteCacheWithName:@"searchResults"];
        [self.fetchedResultsController performFetch:nil];

    }

    return YES; 
}

有什么问题吗？以及如何提高性能？此致。

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1 回答 1

7

使用CONTAINS谓词很慢，特别是在它不区分大小写的情况下。使用两个会使它变得更慢。

Apple 通过实际上不进行全文搜索，使其应用​​程序中的“全文”搜索看起来很快。他们的大多数应用程序都使用前缀搜索，依赖于如果您搜索“Frank”，则不会输入“ran”的概念。此外，它们对属性进行规范化并改为进行基于排序的搜索：例如，如果您有一个firstName内容如“François”的normalizedFirstName属性，则创建一个丢失大小写和变音符号（“francois”）的派生属性。然后您对“法郎”的搜索得到谓词：

normalizedFirstName >= "franc" AND normalizedFirstName < "frand"

这个谓词要快得多。

如果您有一个可以包含多词字符串的属性，并且您想对字符串上的任何单词进行类似的前缀匹配，您可以为关键字创建相关实体并使用子查询来匹配关键字与谓词匹配的实体。

有关详细信息，请参阅 DerivedProperty 示例代码和/或 WWDC 2010 第 137 场会议的视频（均位于 developer.apple.com）。

于 2012-06-26T05:46:20.330 回答