So, if you're a MacOS user and you ever feel the need to get some raw stats about the photos you've taken and stored in your iCloud photo library, there's a (fairly) easy way to dig in.
iPhoto's metadata lives in a giant sqlite database, and you can just… query it. Unless you've moved it, it lives at `~/Pictures/Photos Library.photoslibrary/database/Photos.sqlite`, and quite a bit of interesting stuff is in the ZEXTENDEDATTRIBUTES table.