How to use

parallelDo

method

in

org.apache.crunch.PCollection

 public static <S> PCollection<S> sample(PCollection<S> input, long seed, double probability) {
  String stageName = String.format("sample(%.2f)", probability);
  return input.parallelDo(stageName, new SamplerFn<S>(seed, probability), input.getPType());
 }
}

/**
 * Output records from the given {@code PCollection} using a given seed. Useful for unit
 * testing.
 * 
 * @param input The {@code PCollection} to sample from
 * @param seed The seed for the random number generator
 * @param probability The probability (0.0 < p < 1.0)
 * @return The output {@code PCollection} created from sampling
 */
public static <S> PCollection<S> sample(PCollection<S> input, Long seed, double probability) {
 String stageName = String.format("sample(%.2f)", probability);
 return input.parallelDo(stageName, new SampleFn<S>(probability, seed), input.getPType());
}

@Override
public PCollection<S> union(PCollection<S>... collections) {
 List<PCollectionImpl<S>> internal = Lists.newArrayList();
 internal.add(this);
 for (PCollection<S> collection : collections) {
  internal.add((PCollectionImpl<S>) collection.parallelDo(IdentityFn.<S>getInstance(), collection.getPType()));
 }
 return new UnionCollection<S>(internal);
}

@Override
public PCollection<S> union(PCollection<S>... collections) {
 List<PCollectionImpl<S>> internal = Lists.newArrayList();
 internal.add(this);
 for (PCollection<S> collection : collections) {
  internal.add((PCollectionImpl<S>) collection.parallelDo(IdentityFn.<S>getInstance(), collection.getPType()));
 }
 return pipeline.getFactory().createUnionCollection(internal);
}

/**
 * Transform this LCollection to an {@link LTable} using a standard Crunch {@link DoFn}
 */
default <K, V> LTable<K, V> parallelDo(DoFn<S, Pair<K, V>> fn, PTableType<K, V> pType) {
  return factory().wrap(underlying().parallelDo(fn, pType));
}

/**
 * Transform this LCollection using a standard Crunch {@link DoFn}
 */
default <T> LCollection<T> parallelDo(DoFn<S, T> fn, PType<T> pType) {
  return factory().wrap(underlying().parallelDo(fn, pType));
}

/**
 * Convert the given {@code PCollection<Pair<K, V>>} to a {@code PTable<K, V>}.
 * @param pcollect The {@code PCollection} to convert
 * @return A {@code PTable} that contains the same data as the input {@code PCollection}
 */
public static <K, V> PTable<K, V> asPTable(PCollection<Pair<K, V>> pcollect) {
 PType<Pair<K, V>> pt = pcollect.getPType();
 PTypeFamily ptf = pt.getFamily();
 PTableType<K, V> ptt = ptf.tableOf(pt.getSubTypes().get(0), pt.getSubTypes().get(1));
 DoFn<Pair<K, V>, Pair<K, V>> id = IdentityFn.getInstance();
 return pcollect.parallelDo("asPTable", id, ptt);
}

/**
 * Convert the given {@code PCollection<Pair<K, V>>} to a {@code PTable<K, V>}.
 * @param pcollect The {@code PCollection} to convert
 * @return A {@code PTable} that contains the same data as the input {@code PCollection}
 */
public static <K, V> PTable<K, V> asPTable(PCollection<Pair<K, V>> pcollect) {
 PType<Pair<K, V>> pt = pcollect.getPType();
 PTypeFamily ptf = pt.getFamily();
 PTableType<K, V> ptt = ptf.tableOf(pt.getSubTypes().get(0), pt.getSubTypes().get(1));
 DoFn<Pair<K, V>, Pair<K, V>> id = IdentityFn.getInstance();
 return pcollect.parallelDo("asPTable", id, ptt);
}

@SuppressWarnings("unchecked")
public void write(PCollection<?> pcollection, Target target) {
 if (pcollection instanceof PGroupedTableImpl) {
  pcollection = ((PGroupedTableImpl<?, ?>) pcollection).ungroup();
 } else if (pcollection instanceof UnionCollection || pcollection instanceof UnionTable) {
  pcollection = pcollection.parallelDo("UnionCollectionWrapper",
    (MapFn) IdentityFn.<Object> getInstance(), pcollection.getPType());
 }
 addOutput((PCollectionImpl<?>) pcollection, target);
}

private static <T> PTable<T, Boolean> toTable(PCollection<T> coll) {
 PTypeFamily typeFamily = coll.getTypeFamily();
 return coll.parallelDo(new DoFn<T, Pair<T, Boolean>>() {
  @Override
  public void process(T input, Emitter<Pair<T, Boolean>> emitter) {
   emitter.emit(Pair.of(input, Boolean.TRUE));
  }
 }, typeFamily.tableOf(coll.getPType(), typeFamily.booleans()));
}

@Override
public <T> void writeTextFile(PCollection<T> pcollection, String pathName) {
 pcollection.parallelDo("asText", new StringifyFn<T>(), Writables.strings())
   .write(To.textFile(pathName));
}

private static <T> PTable<T, Boolean> toTable(PCollection<T> coll) {
 PTypeFamily typeFamily = coll.getTypeFamily();
 return coll.parallelDo(new DoFn<T, Pair<T, Boolean>>() {
  @Override
  public void process(T input, Emitter<Pair<T, Boolean>> emitter) {
   emitter.emit(Pair.of(input, Boolean.TRUE));
  }
 }, typeFamily.tableOf(coll.getPType(), typeFamily.booleans()));
}

@Override
public <T> void writeTextFile(PCollection<T> pcollection, String pathName) {
 pcollection.parallelDo("asText", new StringifyFn<T>(), Writables.strings())
   .write(To.textFile(pathName));
}

private static <T> PTable<T, Boolean> toTable(PCollection<T> coll) {
 PTypeFamily typeFamily = coll.getTypeFamily();
 return coll.parallelDo(new DoFn<T, Pair<T, Boolean>>() {
  @Override
  public void process(T input, Emitter<Pair<T, Boolean>> emitter) {
   emitter.emit(Pair.of(input, Boolean.TRUE));
  }
 }, typeFamily.tableOf(coll.getPType(), typeFamily.booleans()));
}

@Override
public <T> void writeTextFile(PCollection<T> pcollection, String pathName) {
 // Ensure that this is a writable pcollection instance.
 pcollection = pcollection.parallelDo("asText", IdentityFn.<T> getInstance(), WritableTypeFamily
   .getInstance().as(pcollection.getPType()));
 write(pcollection, At.textFile(pathName));
}

@Override
public <K, V> PTable<K, V> create(Iterable<Pair<K, V>> contents, PTableType<K, V> ptype, CreateOptions options) {
 if (Iterables.isEmpty(contents)) {
  return emptyPTable(ptype);
 }
 ReadableSource<Pair<K, V>> src = null;
 try {
  src = ptype.createSourceTarget(getConfiguration(), createTempPath(), contents, options.getParallelism());
 } catch (IOException e) {
  throw new CrunchRuntimeException("Error creating PTable: " + contents, e);
 }
 return read(src).parallelDo(IdentityFn.<Pair<K, V>>getInstance(), ptype);
}

 public static <S> PCollection<S> aggregate(PCollection<S> collect, Aggregator<S> aggregator) {
  PTypeFamily tf = collect.getTypeFamily();
  return collect.parallelDo("Aggregate.aggregator", new MapFn<S, Pair<Boolean, S>>() {
   public Pair<Boolean, S> map(S input) {
    return Pair.of(false, input);
   }
  }, tf.tableOf(tf.booleans(), collect.getPType()))
  .groupByKey(1)
  .combineValues(aggregator)
  .values();
 }
}

private static <T> PTable<String, BloomFilter> createFilterTable(PCollection<T> collection, BloomFilterFn<T> filterFn) {
 PTypeFamily tf = collection.getTypeFamily();
 PTable<String, BloomFilter> table = collection.parallelDo(filterFn,
   tf.tableOf(tf.strings(), Writables.writables(BloomFilter.class)));
 return table.groupByKey(1).combineValues(new BloomFilterAggregator());
}

/**
 * Returns a {@code PTable} that contains the unique elements of this collection mapped to a count
 * of their occurrences.
 */
public static <S> PTable<S, Long> count(PCollection<S> collect) {
 PTypeFamily tf = collect.getTypeFamily();
 return collect.parallelDo("Aggregate.count", new MapFn<S, Pair<S, Long>>() {
  public Pair<S, Long> map(S input) {
   return Pair.of(input, 1L);
  }
 }, tf.tableOf(collect.getPType(), tf.longs())).groupByKey()
   .combineValues(Aggregators.SUM_LONGS());
}

private static <E> PCollection<E> partition(PCollection<E> collection,
                      int numReducers) {
 PType<E> type = collection.getPType();
 PTableType<E, Void> tableType = Avros.tableOf(type, Avros.nulls());
 PTable<E, Void> table = collection.parallelDo(new AsKeyTable<E>(), tableType);
 PGroupedTable<E, Void> grouped =
   numReducers > 0 ? table.groupByKey(numReducers) : table.groupByKey();
 return grouped.ungroup().keys();
}