serfn.clj

(defn cascalog-map
  [op-var output-fields & {:keys [stateful?]}]
  (let [ser (ops/fn-spec op-var)]
    (proxy [BaseOperation Function] [^Fields output-fields]
      (prepare [^FlowProcess flow-process ^OperationCall op-call]
        (let [op (serfn/deserialize-val ser)]
          (-> op-call
              (.setContext [op (if stateful? (op))]))))
      (operate [^FlowProcess flow-process ^FunctionCall fn-call]
        (let [[op] (.getContext fn-call)
              collector (-> fn-call .getOutputCollector)
              ^Tuple tuple (-> fn-call .getArguments .getTuple)]
          (->> (Util/coerceFromTuple tuple)
               (apply op)
               (Util/coerceToTuple)
               (.add collector))))
      (cleanup [flow-process ^OperationCall op-call]
        (if stateful?
          (let [[op state] (.getContext op-call)]
            (op state)))))))