| /** |
| * 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.hadoop.mapreduce.lib.join; |
| |
| import java.io.IOException; |
| |
| import org.apache.hadoop.io.Writable; |
| import org.apache.hadoop.io.WritableComparable; |
| import org.apache.hadoop.mapreduce.RecordReader; |
| |
| /** |
| * Additional operations required of a RecordReader to participate in a join. |
| */ |
| public abstract class ComposableRecordReader<K extends WritableComparable<?>, |
| V extends Writable> |
| extends RecordReader<K,V> |
| implements Comparable<ComposableRecordReader<K,?>> { |
| |
| /** |
| * Return the position in the collector this class occupies. |
| */ |
| abstract int id(); |
| |
| /** |
| * Return the key this RecordReader would supply on a call to next(K,V) |
| */ |
| abstract K key(); |
| |
| /** |
| * Clone the key at the head of this RecordReader into the object provided. |
| */ |
| abstract void key(K key) throws IOException; |
| |
| /** |
| * Create instance of key. |
| */ |
| abstract K createKey(); |
| |
| /** |
| * Create instance of value. |
| */ |
| abstract V createValue(); |
| |
| /** |
| * Returns true if the stream is not empty, but provides no guarantee that |
| * a call to next(K,V) will succeed. |
| */ |
| abstract boolean hasNext(); |
| |
| /** |
| * Skip key-value pairs with keys less than or equal to the key provided. |
| */ |
| abstract void skip(K key) throws IOException, InterruptedException; |
| |
| /** |
| * While key-value pairs from this RecordReader match the given key, register |
| * them with the JoinCollector provided. |
| */ |
| @SuppressWarnings("unchecked") |
| abstract void accept(CompositeRecordReader.JoinCollector jc, K key) |
| throws IOException, InterruptedException; |
| } |