On 2014 Jan 20, at 09:50, Sean McBride <s...@rogue-research.com> wrote:

> I opt out of WAL in 
> configurePersistentStoreCoordinatorForURL:ofType:modelConfiguration:storeOptions:error:,
>  but my official buildbot is not actually linking against the 10.9 SDK yet, 
> so my experience may not count for much.

Hmmm, I do it in -[NSPersistentStoreCoordinator 
addPersistentStoreWithType:configuration:URL:options:error:].

OK, I’m making up a demo project to see if I can reproduce this.

> I don't get your comment here.  You don't think users of newer OS X versions 
> expect to be able to move documents around?

The trouble occurs if a developer of an older Core Data app begins to link 
against the 10.9 SDK, and allows the *new* default journal_mode = write-ahead 
logging to be used, but does not migrate the app’s document to use the new 
“file package” format.  As far as the user is concerned, the document file is 
still the sqlite database file.  The user may think that the -shm and -wal 
files, which are occasionally produced by sqlite, and appear along side the 
document file, are junk.  If such a user moves the document file without moving 
the -shm or -wal file, or trashes the -shm or -wal file, data corruption can 
occur.

So, that is why Apple provided the new option to opt out of write-ahead 
logging, and why it is important that it works in all cases.



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