| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you 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. |
| */ |
| package org.apache.crunch; |
| |
| import java.io.Serializable; |
| import java.math.BigInteger; |
| import java.util.LinkedList; |
| import java.util.List; |
| import java.util.SortedSet; |
| |
| import org.apache.crunch.fn.Aggregators; |
| import org.apache.crunch.util.Tuples; |
| import org.apache.hadoop.conf.Configuration; |
| |
| import com.google.common.base.Joiner; |
| import com.google.common.collect.ImmutableList; |
| import com.google.common.collect.Lists; |
| import com.google.common.collect.Sets; |
| |
| /** |
| * A special {@link DoFn} implementation that converts an {@link Iterable} of |
| * values into a single value. If a {@code CombineFn} instance is used on a |
| * {@link PGroupedTable}, the function will be applied to the output of the map |
| * stage before the data is passed to the reducer, which can improve the runtime |
| * of certain classes of jobs. |
| * <p> |
| * Note that the incoming {@code Iterable} can only be used to create an |
| * {@code Iterator} once. Calling {@link Iterable#iterator()} method a second |
| * time will throw an {@link IllegalStateException}. |
| */ |
| public abstract class CombineFn<S, T> extends DoFn<Pair<S, Iterable<T>>, Pair<S, T>> { |
| } |