ios - Core Data design principles

Question

I just started reading this guide: https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/CoreData/KeyConcepts.html#//apple_ref/doc/uid/TP40001075-CH30-SW1

And it basically has (in my opinion) two big contradictions:

I get them both, but basically, if I follow the first "implement a custom class to the entity from which classes representing subentities also inherit"-statement, then ALL my entities will be put in the same table. Which could cause performance issues, according to the NOTE.

How big of a performance hit would I run into of it create a "custom super entity"?

Answer 1

I'm not familiar with this quirk of SQLite, but modeling base class/subclass relationships are usually done with different tables. There is one table that represents the base class which contains attributes common to all derivative classes (Vehiclea) and a different table for each subclass which contain attributes unique to that subclass (Cars, Trains, Airplanes).

Performance is no better or worse than any entity normalized across different tables.