Crash while executing fetch request

I had a crash while executing executeFetchRequest:error:

MyApp[595] has active assertions beyond permitted time:

{(
    <SBProcessAssertion: 0x1e5d1260> identifier: Suspending process: MyApp[595] 
permittedBackgroundDuration: 10.000000 reason: suspend owner pid:29 preventSuspend
  preventThrottleDownCPU  preventThrottleDownUI

And this is my 开发者_开发知识库code:

NSString *predString = [NSString stringWithFormat:@"categoryId MATCHES '%@'", categoryId];
NSPredicate *predicate = [NSPredicate predicateWithFormat:predString];
[request setPredicate:predicate];
NSError *error = nil;
NSArray* objects = [context executeFetchRequest: request error: &error];

As far as I understand, the fetch, done synchronously in the main thread, took too much time, more than 10 secs, and the process was suspended.

Browsing in internet I found this nice solution to make the fetch async:

http://blog.zssz.me/2010/01/asynchronous-fetch-in-core-data.html

But i am wondering if actually my assumption is correct, and if there are simpler solutions to this problem. Thanks a lot.

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You can't use the MATCHES operator with an SQL store (which you are almost certainly using) because sqlite does not support regex. I would have expected it to error out instead of timing out but apparently not.

You want to use CONTAINS or even better, ==. If you have an attribute called catergoryID it usually denotes an attribute with a specific unique value and not one that has a lot of minor variations. Using ==/equals will produce a vastly faster fetch.

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The error is pretty clear :)

I'd try it in a background thread and see what happens.