I have an application with a very large Core database. Last year I repeatedly powered it.
The last time I executed the database version, I made one simple change to the object: I added a new optional attribute. For some reason, it will not migrate using Light-weight Migration. I found out much later that this was due to an error in the Apple Lightweight Migration code resulting from the "renaming of identifiers" that I needed in another version.
Anyway, I'm distracted ...
Due to an error due to which I did not use Light-weight migration, I created a mapping file to help with the migration, not realizing that it will be a much more difficult process and will make my users wait while the application loads the entire database into memory during migration. It turns out that this is not at all an option with very large databases, and many of my users could not migrate the database at all because of memory problems, etc.
So now I want to republish my application and clarify this problem. The problem is that some of my users have a database that is somehow labeled "mid-migration." Even with my new code, which gets rid of the mapping file and supports lightweight migration, users in this state “in the middle of the migration” do not seem to receive a reset.
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