Datomic: memoized predicate functions

gistfile1.clj

;; see http://stackoverflow.com/questions/16386793/datomic-query-function-that-filters-and-binds

(require '[datomic.api :as d])
(def uri "datomic:mem://test")
(d/create-database uri)
(def conn (d/connect uri))

;; sample attribute definiton
(d/transact conn [{:db.install/_attribute :db.part/db
                   :db/id #db/id[:db.part/db]
                   :db/ident :user/regex-match
                   :db/valueType :db.type/string
                   :db/cardinality :db.cardinality/one}])
 
;; sample data
(d/transact conn [{:db/id #db/id[:db.part/user] :user/regex-match "so 1"}
                  {:db/id #db/id[:db.part/user] :user/regex-match "no-match"}
                  {:db/id #db/id[:db.part/user] :user/regex-match "so 23"}
                  {:db/id #db/id[:db.part/user] :user/regex-match "no-match 2"}
                  {:db/id #db/id[:db.part/user] :user/regex-match "so 456"}])

(defn match? [m] (re-find (re-pattern "so (\\d+)") m))

(def fast-match? (memoize match?))

(->> (d/datoms (d/db conn) :aevt :user/regex-match)
     (filter #(fast-match? (:v %)))
     (map :v))