hadoop ComposableRecordReader 源码
haddop ComposableRecordReader 代码
文件路径：/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/lib/join/ComposableRecordReader.java
/**
* 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.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
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.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
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;
}
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