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Core Data in Swift by Marcus S. Zarra

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A Heavy/Manual Migration

A heavy migration is required when we go outside of the bounds of what a light migration can accomplish. A simple example of something that goes beyond a light migration is a logic-based migration. Imagine a situation in which, as part of a migration/application update, we need to change the data that’s in the database. Perhaps there’s a typo in the included data or a change in the logic. Changing the data during the migration is outside the scope of a light migration. However, we can easily add it to a heavy migration.

A more complex example would be a situation that involves normalizing data. In our application, each recipe has one or more recipe ingredients. If we wanted to expand our application and extract the common ...

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