devnewb.clj

(ns devnewb
  (:require [datomic.api :as d :refer (db q)]
            [clojure.data.generators :as gen]))

;; Make sure a free transactor is running at URI below
(def uri "datomic:free://localhost:4334/devnewb")

;; Caution!!!  This happens on load!
(d/delete-database uri)


(d/create-database uri)
(def conn (d/connect uri))

@(d/transact
  conn
  [{:db/id                 (d/tempid :db.part/db)
    :db/ident              :foo
    :db/valueType          :db.type/ref
    :db/cardinality        :db.cardinality/one
    :db.install/_attribute :db.part/db}
   {:db/id                 (d/tempid :db.part/db)
    :db/ident              :bar
    :db/valueType          :db.type/keyword
    :db/cardinality        :db.cardinality/one
    :db.install/_attribute :db.part/db}])

(def tempids (map (partial d/tempid :db.part/user)
                  (range -1 -150001 -1)))

(def parent-count 5)

;; Create parents
@(d/transact conn (map #(hash-map :db/id %
                                  :bar   (gen/keyword)) (take parent-count tempids)))

(def parent-entities (map first
                  (q '[:find ?e
                       :where [?e :bar]]
                     (db conn))))

(defn gen-entity
  "Generates an entity with the given id, where id is element of
  tempids."
  [id]
  {:db/id id
   :bar   (gen/keyword)
   :foo   (gen/rand-nth parent-entities)})

(def entities (map gen-entity (drop parent-count tempids)))

(defn -main
  [& args]
  (doseq [tx (partition 1000 entities)]
    (d/transact-async conn tx))

  (println)
  (println "Cold:")
  (println)
  (doseq [parent parent-entities]
    (time
     (count
      (q '[:find ?e :in $ ?r :where [?e :foo ?r] [?e :bar]]
         (db conn)
         parent))))

  (println)
  (println "Warm:")
  (println)
  (doseq [parent parent-entities]
    (time
     (count
      (q '[:find ?e :in $ ?r :where [?e :foo ?r] [?e :bar]]
         (db conn)
         parent))))
  )

stdout

Cold:

"Elapsed time: 914.685 msecs"
"Elapsed time: 349.759 msecs"
"Elapsed time: 312.492 msecs"
"Elapsed time: 309.515 msecs"
"Elapsed time: 205.903 msecs"

Warm:

"Elapsed time: 202.668 msecs"
"Elapsed time: 193.455 msecs"
"Elapsed time: 214.274 msecs"
"Elapsed time: 202.884 msecs"
"Elapsed time: 206.809 msecs"
nil