(Rough) total JVM memory size of the log

log_size.clj

;; bin/run log_size.clj DB-URI t

;; Estimates the total in-memory size of all log entries from t to end of data.
;; Scans log from t to the end, so run against a backup instead of production if possible!

(require
 '[clojure.edn :as edn]
 '[clojure.pprint :as pp]
 '[datomic.api :as d]
 '[datomic.memory-size :as size])

(defn log-size*
  [conn t]
  (let [log (d/log conn)
        db (d/db conn)]
    (->> (d/tx-range log t nil)
         (reduce (fn [size logentry]
                   (+ size (size/memory-size logentry)))
                 0))))

(defn log-size
  "Returns estimate of log memory size from t to end of data"
  [uri t]
  (let [conn (d/connect uri)]
    (log-size* conn t)))

(try
 (let [[db-uri t] *command-line-args*]
   (prn (log-size db-uri (edn/read-string t))))
 (finally
  (d/shutdown true)))