CoreData migrations without versioning

Question

Right now I use versioning to make any changes in a database. But it brings some problems. For example it's hard to merge a feature branch with a new db version into a master/dev where somebody also added a new version.

So my question: Is it safe to change db in a single xcdatamodel without adding new versions? I tried so and it works but everywhere on the internet I see warnings that you must not do that.

iOS9+.

I found this: https://stackoverflow.com/a/37264096/5328417 but it's without a proof

@TomHarrington adding/removing tables, adding/removing columns, renaming — Arsen, Nov 22 '17 at 06:05
See the [WWDC video](https://developer.apple.com/videos/play/wwdc2015/220/) from Session 220 in 2015, from about 18’15. There’s a discussion about model caching. — pbasdf, Nov 22 '17 at 09:10

score 10 · Accepted Answer · answered Oct 19 '18 at 08:16

As @pbasdf noted, since iOS 9 you can do a lightweight migration without adding any new model version. Source model (previous model version) is cached to store and used as a last ditch effort during lightweight migration.

I am using this feature in my own apps successfully. Although I was not able to find this documented. Just that WWDC video (18'15 Model Caching) mentioned. This is exactly the reason why Core Data is so mysterious sometimes..

score 0 · Answer 2 · answered Nov 22 '17 at 09:22

0

If your app is in development stage then you may use one model without versioning.

But if it is release on the App Store then you have to create the versions when you make changes (such as adding a new attribute, adding a new entity, renames attributes etc.). Otherwise, Core Data won't perform lightweight migration.

answered Nov 22 '17 at 09:22

Oleg

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Evenmore, it will crash when performing migration. – kirander Nov 22 '17 at 09:50
Are you sure that you pass during initialization Core Data Stack these options`NSMigratePersistentStoresAutomaticallyOption: true, NSInferMappingModelAutomaticallyOption: true`? – Oleg Nov 22 '17 at 09:55
What do you want to say? – kirander Nov 22 '17 at 09:57
Check out a comment from @pbasdf. It looks like it must work without creating a new version – Arsen Nov 22 '17 at 11:25

CoreData migrations without versioning

2 Answers2