Core data issues with refactoring an entity

We have an entity called "EMail" with attributes such as ID, From, To, Subject, Body.

Due to various reasons including performance for retrieval, impact on migration etc, we want to refactor this entity into two entities with a parent child relationship: "EMail": ID, From, To, Subject and "EMailBody": ID, Body.

Can this be done with an existing model? If so, will this still fall under lightweight migration?

Core data issues with refactoring an entity
 
 
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