After you upgrade to iOS 11, your device may be slow for a while. Besides re-indexing, the Photos app needs to analyze your photos using Machine Learning.
Give it a chance to finish its work, and performance should be good.
I also have an iPad Air 2 running iOS 11.0.1
You possibly have a good point. I don't keep any photos in the Apple system, they're all on Google, so the re-indexing you suggest will not have occurred in my Air 2. Must say I'm liking how the dock and split-screen work in iOS 11.