Cannot seem to custom migrate with mapping models because tables are not updated

[jasper-ch-chan]

I was wondering if anyone has tried using Migration policies to perform a custom migration? I am currently struggling with this as I've noticed when executeFetchRequest gets called and it tries to insert my migrated data (which is correct) into the context, the entity table attributes haven't been updated yet and thus, causing a failure.

[jasper-ch-chan]

@sascha I know you were able to overcome some migration issues with custom migration. Would you be able to shed some light as to how you were able to overcome this issue?

[sascha]

@jasper-ch-chan I've only really used lightweight migrations so far (NSMigratePersistentStoresAutomaticallyOption, NSInferMappingModelAutomaticallyOption), but may need support for custom migrations soon. I'm afraid the issue I described at #14 still exists, so this is probably a rather complex task.

[jasper-ch-chan]

@gavin-black Could we get some support with regards to custom migrations? This is becoming a pretty critical issue for our software as well.

[jasper-ch-chan]

@sascha Just for your information, I made a simple little playground to do all my ECD testing. Feel free to fork and use it as your experimentation project too!

https://github.com/sdwornik/ECD-Migration

[gavin-black]

Hi @jasper-ch-chan,

Unfortunately I don't feel equipped to really help with this. I've never used custom migrations, let alone going through under the hood to really implement everything myself. I do remember reading about the set of possible operations that are supported a while back (transform, add, etc.). But actually learning migrations, adding in support for each method of migration, testing them properly, while making sure I don't clobber anything else, is unlikely in any sane amount of time. Definitely will help with any questions or pull requests, but outside of that I'm not sure what support I can offer.

-- Gavin

[jasper-ch-chan]

@dorada Will we be able to get some assistance with this regards? I've figured out that essentially, metadataForPersistentStoreOfType:URL:error: is returning nil as it is not implemented in ECD.

[DanielBroad]

My employer doesn't use custom migrations, so I can't justify writing the code for you.

Happy to review any pull request.