Database Reference
In-Depth Information
Figure 9—Versions 1 and 2 of the data model
A heavy migration is far more complicated than a light migration. When we
perform a heavy migration, we must load each entity into memory, translate
it from the old store to the new store, and then write it back out to disk. This
requires two Core Data “stacks” in memory at the same time and a large
amount of data processing in our application. It takes time—a lot of time.
When a heavy migration is required, the application normally needs to show
a wait dialog to the user so that the user knows what's going on.
