@mrchance that should work. I'm guessing the value you're looking for isn't the symbol foo, but rather what the value foo is bound to? Trying removing the quote before the vector. Is :unique/name set to unique in the schema?

(-> db :schema :unique/name)
;; should contain :db/unique with either 
;; :db.unique/identity or :db.unique/value

I think you also can use (d/entid db [:unique/name foo]) to get the id directly

@petterik thanks, I'll try that. I only need the id, and yes, it's unique in the schema