sql.clj

(defn with-query-results-cursor
  "Execute a query using a cursor to efficiently handle large data
  sets. result-fn will be applied to a result set seq."
  [[sql & params :as sql-params] fetch-size result-fn]
  (sql/transaction
   (with-open [stmt (.prepareStatement (sql/connection) sql)]
     (doseq [[index value] (map vector (iterate inc 1) params)]
       (.setObject stmt index value))
     (.setFetchSize stmt fetch-size)
     (with-open [rset (.executeQuery stmt)]
       (result-fn (resultset-seq rset))))))

(defn exec-batched
  [conn query batch-size batch-fn]
  (sql/with-connection conn
    (with-query-results-cursor
      query
      batch-size
      (fn [rs]
        (doseq [batch (partition batch-size batch-size nil rs)]
          (batch-fn batch))))))

usage.clj

(exec-batched conn 
              ["SELECT * FROM ... WHERE x = ?" 42]
              100
              (fn [rows]
                (doseq [row rows]
                  (println row)))