Prepopulated Core Data SQL store with new Write-Ahead Log (WAL) journaling

Question

I would like to ship my app with an SQL datastore, but now, since Apple has introduced a WAL journaling, that makes 3 files instead of one, so I wonder if I should ship all 3 of them, or I can try to force SQL to make a checkpoint, merging it all into one .sql file.

I would really like to go with this new iOS 7 feature, so going back to rollback journaling is not a way for me.

Answer 1

To force SQLite to make a checkpoint, execute PRAGMA wal_checkpoint.

Alternatively, ship the database with journal_mode = DELETE, and change the mode after the file has been installed.

In any case, there is no problem with just shipping all files. (The -shm file does not contain permanent data and could be ignored.)

Answer 2

You don't have to use WAL, that's just the default. You can switch to a different mode. When adding the persistent store, set the options argument to something like

NSDictionary *options = @{ @"journal_mode": @"DELETE" };

Then you'll get the same journal behavior as in earlier versions of iOS. Use this when creating your pre-populated data store and you won't need to deal with the extra journal files.