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;;
;;
;; Copyright 2015 Netflix, Inc.
;;
;; Licensed under the Apache License, Version 2.0 (the "License");
;; you may not use this file except in compliance with the License.
;; You may obtain a copy of the License at
;;
;; http://www.apache.org/licenses/LICENSE-2.0
;;
;; Unless required by applicable law or agreed to in writing, software
;; distributed under the License is distributed on an "AS IS" BASIS,
;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
;; See the License for the specific language governing permissions and
;; limitations under the License.
;;
;;
(ns pigpen.cascading.runtime
(:import (java.util List)
(org.apache.hadoop.io BytesWritable)
(cascading.operation OperationCall FunctionCall
BufferCall AggregatorCall)
(cascading.tuple Fields Tuple TupleEntry TupleEntryCollector)
(pigpen.cascading OperationUtil SingleIterationSeq))
(:require [taoensso.nippy :refer [freeze thaw]]
[pigpen.runtime :as rt :refer [HybridToClojure]]
[schema.core :as s]
[pigpen.model :as m]))
(set! *warn-on-reflection* true)
;; ******** Serialization ********
(extend-protocol HybridToClojure
BytesWritable
(rt/hybrid->clojure [value]
(-> value
(OperationUtil/getBytes)
(thaw {:compressor nil
:encryptor nil
:v1-compatibility? false}))))
(defn cs-freeze [value]
(BytesWritable. (freeze value {:compressor nil, :skip-header? true})))
(defn ^:private cs-freeze-with-nils [value]
(if-not (nil? value)
(cs-freeze value)))
(defmethod pigpen.runtime/post-process [:cascading :native]
[_ _]
identity)
(defmethod pigpen.runtime/post-process [:cascading :frozen]
[_ _]
(fn [args]
(map cs-freeze args)))
(defmethod pigpen.runtime/post-process [:cascading :frozen-with-nils]
[_ _]
(fn [args]
(map cs-freeze-with-nils args)))
(defmethod pigpen.runtime/post-process [:cascading :native-key-frozen-val]
[_ _]
(fn [[key value]]
[key (cs-freeze value)]))
(defn ^:private ^Tuple ->tuple [^List l]
(Tuple. (.toArray l)))
(defn add-tuple
"Adds a tuple to the collector; returns the collector."
[^TupleEntryCollector collector ^Tuple tuple]
(doto collector
(.add tuple)))
;; ******** Prepare ********
(defn prepare-expr [expr]
(case (:type expr)
:field expr
:code (-> expr
(update-in [:init] pigpen.runtime/eval-string)
(update-in [:func] pigpen.runtime/eval-string))))
(defn prepare-projection [p]
(when p
(update-in p [:expr] prepare-expr)))
(defn prepare-projections [ps]
(mapv prepare-projection ps))
(defn prepare
"Called from UDFs to deserialize clojure data structures"
[context]
(-> context
pigpen.runtime/eval-string
(update-in [:projections] prepare-projections)
(update-in [:func] prepare-projection)))
(def prepare (memoize prepare))
;; ******** Func ********
(defn field-lookup [values arg]
(cond
(string? arg) arg
(symbol? arg) (values arg)
:else (throw (ex-info "Unknown arg" {:arg arg, :values values}))))
(s/defn eval-field
[values {:keys [alias expr :- m/FieldExpr]} :- m/Projection]
(let [{:keys [field]} expr]
[alias (values field)]))
(s/defn eval-func
[values
{:keys [expr alias]} :- m/Projection
init
reducef]
(let [{:keys [func args]} expr
arg-values (mapv (partial field-lookup values) args)]
((func reducef) init arg-values)))
(defn function-operate
"Called from pigpen.cascading.PigPenFunction"
[^FunctionCall function-call]
(let [{:keys [field-projections func fields]} (.getContext function-call)
values (fn [f]
(-> function-call
(.getArguments)
(.getObject (pr-str f))
rt/hybrid->clojure))
field-values (->> field-projections
(map (partial eval-field values))
(into {}))]
(eval-func values func
(.getOutputCollector function-call)
(fn [collector fn-result]
(let [result (merge field-values (zipmap (:alias func) fn-result))
tuple (->tuple (mapv result fields))]
(add-tuple collector tuple))))))
;; ******** CoGroup ********
(defn induce-sentinel-nil
"Induces a sentinel per-relation nil value to match pigpen's join behavior.
Called from pigpen.cascading.InduceSentinelNils"
[^FunctionCall function-call
index] ; the index of the relation in the cogroup
(let [entry (.getArguments function-call)
output-collector (.getOutputCollector function-call)]
(if (or (nil? index)
(not (nil? (.getObject entry 0))))
(.add output-collector entry)
(.add output-collector
(doto (Tuple.)
(.add (BytesWritable. (byte-array [index])))
(.add (.getObject entry 1)))))))
(defn remove-sentinel-nil
"Revert the sentinel nils introduced by `induce-sentinel-nil`"
;; Assumes that a frozen user value will alwyas be more than 1 byte
[^BytesWritable v]
(when (and v (< 1 (.getLength v)))
v))
(defn field-indexes
"Takes an array of Fields and creates a lookup from arg -> [iterator, tuple index]"
[value-fields]
(->> value-fields
(map-indexed
(fn [iterator-index ^Fields fields]
(->> fields
(map-indexed
(fn [field-index f]
[(symbol f) [iterator-index field-index]])))))
(apply concat)
(into {})))
(defn arg->value
"For a given arg, finds the value as an iterator or group key"
[^BufferCall buffer-call folds field-indexes arg]
(let [fold-selector (if (contains? folds arg)
first
seq)]
(if-let [[iterator-index field-index] (get field-indexes arg)]
(as-> buffer-call %
(.getJoinerClosure %)
(.getIterator % iterator-index)
(SingleIterationSeq/create %)
(map #(.getObject ^Tuple % field-index) %)
(map rt/hybrid->clojure %)
(fold-selector %))
;else group
(->> buffer-call
(.getGroup)
(.getTuple)
(some identity)
remove-sentinel-nil
rt/hybrid->clojure))))
(defn group-operate
"Called from pigpen.cascading.GroupBuffer"
[^BufferCall buffer-call]
(let [{:keys [args required rename-fields folds func fields]} (.getContext buffer-call)
;; where to find the arg values in the data
field-indexes (-> buffer-call
(.getJoinerClosure)
(.getValueFields)
(field-indexes))
;; fetch the values for the args
values (memoize
(fn [arg]
(let [arg' (get rename-fields arg arg)]
(arg->value buffer-call folds field-indexes arg'))))]
;; when we have all required values, apply the user function
(when (every? values required)
(eval-func values func
(.getOutputCollector buffer-call)
(fn [collector fn-result]
(let [result (zipmap (:alias func) fn-result)
tuple (->tuple (mapv result fields))]
(add-tuple collector tuple)))))))
;; ******** Reduce ********
(defn reduce-operate
"Called from pigpen.cascading.ReduceBuffer"
[^BufferCall buffer-call]
(let [{:keys [func fields]} (.getContext buffer-call)
values (->> buffer-call
(.getArgumentsIterator)
(SingleIterationSeq/create)
(map (fn [^TupleEntry e]
(rt/hybrid->clojure (.getObject e 0))))
constantly)]
(eval-func values func
(.getOutputCollector buffer-call)
(fn [collector fn-result]
(let [result (zipmap (:alias func) fn-result)
tuple (->tuple (mapv result fields))]
(add-tuple collector tuple))))))
;; ******** Fold ********
; Called from pigpen.cascading.PigPenAggregateBy
(defn context->fold-fn [context part]
(get-in context [:projections 0 :expr :func part]))
(defn aggregate-partial-aggregate
[context ^TupleEntry args ^Tuple agg]
(if-not agg
(let [combinef (context->fold-fn context :combinef)]
(recur context args (->tuple [(combinef)])))
(let [pre (context->fold-fn context :pre)
reducef (context->fold-fn context :reducef)
agg (.getObject agg 0)]
(->>
(.getObject args 0)
rt/hybrid->clojure
vector
pre
(reduce reducef agg)))))
(defn aggregate-partial-complete
[^Tuple agg]
(-> agg
(.getObject 0)
cs-freeze
vector
->tuple))
(defn aggregate-final-start
[context ^AggregatorCall aggregator-call]
(let [combinef (context->fold-fn context :combinef)]
(combinef)))
(defn aggregate-final-aggregate
[context ^AggregatorCall aggregator-call]
(let [combinef (context->fold-fn context :combinef)
agg (.getContext aggregator-call)
arg (-> aggregator-call
(.getArguments)
(.getObject 0)
rt/hybrid->clojure)]
(combinef agg arg)))
(defn aggregate-final-complete
[context ^AggregatorCall aggregator-call]
(let [post (context->fold-fn context :post)
agg (.getContext aggregator-call)
value (-> agg
post
cs-freeze
vector
->tuple)]
(-> aggregator-call
(.getOutputCollector)
(.add value))))