001/* 002 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved. 003 * 004 * Project and contact information: http://www.cascading.org/ 005 * 006 * This file is part of the Cascading project. 007 * 008 * Licensed under the Apache License, Version 2.0 (the "License"); 009 * you may not use this file except in compliance with the License. 010 * You may obtain a copy of the License at 011 * 012 * http://www.apache.org/licenses/LICENSE-2.0 013 * 014 * Unless required by applicable law or agreed to in writing, software 015 * distributed under the License is distributed on an "AS IS" BASIS, 016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 017 * See the License for the specific language governing permissions and 018 * limitations under the License. 019 */ 020 021package cascading.tuple.collect; 022 023import java.util.Collection; 024import java.util.Map; 025 026import cascading.provider.CascadingFactory; 027import cascading.tuple.Tuple; 028 029/** 030 * Interface TupleMapFactory allows developers to plugin alternative implementations of a "tuple map" 031 * used to back in memory "join" and "co-group" operations. Typically these implementations are 032 * "spillable", in that to prevent using up all memory in the JVM, after some threshold is met or event 033 * is triggered, values are persisted to disk. 034 * <p/> 035 * The {@link Map} classes returned must take a {@link cascading.tuple.Tuple} as a key, and a {@link Collection} of Tuples as 036 * a value. Further, {@link Map#get(Object)} must never return {@code null}, but on the first call to get() on the map 037 * an empty Collection must be created and stored. 038 * <p/> 039 * That is, {@link Map#put(Object, Object)} is never called on the map instance internally, 040 * only {@code map.get(groupTuple).add(valuesTuple)}. 041 * <p/> 042 * Using the {@link TupleCollectionFactory} to create the underlying Tuple Collections would allow that aspect 043 * to be pluggable as well. 044 * <p/> 045 * If the Map implementation implements the {@link Spillable} interface, it will receive a {@link Spillable.SpillListener} 046 * instance that calls back to the appropriate logging mechanism for the platform. This instance should be passed 047 * down to any child Spillable types, namely an implementation of {@link SpillableTupleList}. 048 * <p/> 049 * The default implementation for the Hadoop platform is the {@link cascading.tuple.hadoop.collect.HadoopTupleMapFactory} 050 * which created a {@link cascading.tuple.hadoop.collect.HadoopSpillableTupleMap} instance. 051 * <p/> 052 * The class {@link SpillableTupleMap} may be used as a base class. 053 * 054 * @see SpillableTupleMap 055 * @see cascading.tuple.hadoop.collect.HadoopTupleMapFactory 056 * @see TupleCollectionFactory 057 * @see cascading.tuple.hadoop.collect.HadoopTupleCollectionFactory 058 */ 059public interface TupleMapFactory<Config> extends CascadingFactory<Config, Map<Tuple, Collection<Tuple>>> 060 { 061 String TUPLE_MAP_FACTORY = "cascading.factory.tuple.map.classname"; 062 }