What are Fetch Index Elements in the CoreData Model?

ios xcode core-data entity xcdatamodel

Fetch Index Elements are part of Apple’s new indexing API, announced at WWDC 2017. They allow you to specify one or more Index Elements; properties that are used to create an index for faster database searches. In your case, the "title" property will be used to create an index called “compoundIndex” under your "Passage" entity, allowing for faster title searches.

Announcement:https://developer.apple.com/videos/play/wwdc2017/210/?time=628

Demo:https://developer.apple.com/videos/play/wwdc2017/210/?time=997

Documentation (scroll down to "Working with Indexes"):https://developer.apple.com/documentation/coredata/nsmanagedobjectmodel