Querying DataScript database for entities with 3+ tags

user.clj

(require '[datascript :as d])

(defn count-vals [db e a]
  (count (d/datoms db :eavt e a)))
  
(let [db (-> (d/empty-db {:link/tags {:db/cardinality :db.cardinality/many}})
             (d/db-with [[:db/add 1 :link/tags "a"]
                         [:db/add 1 :link/tags "b"]
                         [:db/add 1 :link/tags "c"]
                         [:db/add 2 :link/tags "x"]
                         [:db/add 2 :link/tags "y"]
                         [:db/add 3 :link/tags "q"]
                         [:db/add 3 :link/tags "p"]
                         [:db/add 3 :link/tags "r"]]))]
  (d/q '[:find [?e ...]
         :in $ ?count-vals
         :where [?e :link/tags]
                [(?count-vals $ ?e :link/tags) ?vsc]
                [(>= ?vsc 3)]]
       db count-vals))