How can I reset the faces database in Apple Photos

Select the People album, then Select All. Press delete. Instead of deleting the photos, the app will ask if you want to reset all your names/faces data. I just did it myself and it finally ended an aggravating issue where completely different people had accidentally been merged together.

Word of warning- it's going to take a lot of effort to get the face algorithms back up to speed again.

Credit: Resetting People Album in the new Apple Photos – Rick from Baltimore – Podfeet Podcasts

There is an iPhone forum for IOS questions - High Sierra is to released until 10/25 so there is nothing to discuss re Photos for Mac

The Preview macOS High Sierra - Apple indicates many changes in faces so it may very well do a new total scan - until it is released no one knows

LN