(def client (connect :replica-set [{:host "localhost"
                                    :port 27017
                                    :opts {:read-preference :primary}}]))
(def test-db (get-db client "test_driver"))

(def mongo-coll "mongo")

(query test-db mongo-coll {} :sort-by {:age 1})

(count-docs test-db mongo-coll {:age {:$lt 10}})

(count-docs test-db mongo-coll {})

(doseq [i (range 10)]
  (insert test-db mongo-coll {:id i
                              :name (str "user-" i)
                              :age (rand-int 20)
                              :dob (java.util.Date.)} :multi? false))

(fetch-one test-db mongo-coll {:id 3} :only [:name])

(delete test-db mongo-coll {:age {:$gt 10}})

(update test-db mongo-coll {:age {:$lt 10}} {:$inc {:age 1}})

;; For using multi-document transactions,

(try
    (delete test-db "a" {})
    (delete test-db "b" {})
    ;; Creating new collections is not supported
    ;; in Mongo 4.0 so ensure that there exist collections
    ;; a and b
    (insert test-db "a" {:id 1})
    (insert test-db "b" {:id 1})

    (run-in-transaction client
                        (fn [session]
                          ;; DO NOT ADD try-catch here. If you do this, exceptions
                          ;; will not percolate to the transaction and it will get committed
                          ;; successfully
                          (insert test-db "a" {:a 42} :session session)
                          ;; This will throw an exception
                          (insert test-db "b" {:b (.toString nil)} :session session))
                        {:transaction-opts {:retry-on-errors true}})
    (catch Exception e
      (println "Data in collection a " (query test-db "a" {}))))