Re: CoreData fetch is way too slow

FROM : Phil
DATE : Tue Feb 05 20:52:15 2008

On Feb 5, 2008, at 2:31 PM, James Hober wrote:

> I have a CoreData app that has a SQLite store holding 157,273 
> managed objects.  Each managed object has 2 attributes, input and 
> answer, which are NSStrings and that's all.  No other attributes. 
> No relationships.  No fetched properties.
>
> A simple fetch for a single managed object takes 7 seconds!
>
>    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"%K 
> like %@",
>        @"input", input]; //assume NSString *input exists


Two things come to mind:
First, make sure that 'input' is indexed.
Second, be careful of how/when you use 'like' in your predicates as it 
is pretty easy to take a huge performance hit (this is true even when 
using straight SQL) as you can have a clause that requests "input like 
'%sometext'" which can't make use of an index and you'll force a full 
table scan.

I found Ben's response to one of my posts a few weeks back quite 
helpful: http://www.cocoabuilder.com/archive/message/cocoa/2008/1/16/196552

Phil