/**
* 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.conf.Configuration;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.WritableComparator;
import org.apache.hadoop.mapreduce.InputSplit;
import org.apache.hadoop.mapreduce.RecordReader;
import org.apache.hadoop.mapreduce.TaskAttemptContext;
import org.apache.hadoop.util.ReflectionUtils;
/**
* Proxy class for a RecordReader participating in the join framework.
*
* This class keeps track of the "head" key-value pair for the
* provided RecordReader and keeps a store of values matching a key when
* this source is participating in a join.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public class WrappedRecordReader<K extends WritableComparable<?>,
U extends Writable> extends ComposableRecordReader<K,U> {
protected boolean empty = false;
private RecordReader<K,U> rr;
private int id; // index at which values will be inserted in collector
protected WritableComparator cmp = null;
private K key; // key at the top of this RR
private U value; // value assoc with key
private ResetableIterator<U> vjoin;
private Configuration conf = new Configuration();
@SuppressWarnings("unchecked")
private Class<? extends WritableComparable> keyclass = null;
private Class<? extends Writable> valueclass = null;
protected WrappedRecordReader(int id) {
this.id = id;
vjoin = new StreamBackedIterator<U>();
}
/**
* For a given RecordReader rr, occupy position id in collector.
*/
WrappedRecordReader(int id, RecordReader<K,U> rr,
Class<? extends WritableComparator> cmpcl)
throws IOException, InterruptedException {
this.id = id;
this.rr = rr;
if (cmpcl != null) {
try {
this.cmp = cmpcl.newInstance();
} catch (InstantiationException e) {
throw new IOException(e);
} catch (IllegalAccessException e) {
throw new IOException(e);
}
}
vjoin = new StreamBackedIterator<U>();
}
public void initialize(InputSplit split,
TaskAttemptContext context)
throws IOException, InterruptedException {
rr.initialize(split, context);
conf = context.getConfiguration();
nextKeyValue();
if (!empty) {
keyclass = key.getClass().asSubclass(WritableComparable.class);
valueclass = value.getClass();
if (cmp == null) {
cmp = WritableComparator.get(keyclass);
}
}
}
/**
* Request new key from proxied RR.
*/
@SuppressWarnings("unchecked")
public K createKey() {
if (keyclass != null) {
return (K) ReflectionUtils.newInstance(keyclass, conf);
}
return (K) NullWritable.get();
}
@SuppressWarnings("unchecked")
public U createValue() {
if (valueclass != null) {
return (U) ReflectionUtils.newInstance(valueclass, conf);
}
return (U) NullWritable.get();
}
/** {@inheritDoc} */
public int id() {
return id;
}
/**
* Return the key at the head of this RR.
*/
public K key() {
return key;
}
/**
* Clone the key at the head of this RR into the object supplied.
*/
public void key(K qkey) throws IOException {
ReflectionUtils.copy(conf, key, qkey);
}
/**
* Return true if the RR- including the k,v pair stored in this object-
* is exhausted.
*/
public boolean hasNext() {
return !empty;
}
/**
* Skip key-value pairs with keys less than or equal to the key provided.
*/
public void skip(K key) throws IOException, InterruptedException {
if (hasNext()) {
while (cmp.compare(key(), key) <= 0 && next());
}
}
/**
* Add an iterator to the collector at the position occupied by this
* RecordReader over the values in this stream paired with the key
* provided (ie register a stream of values from this source matching K
* with a collector).
*/
@SuppressWarnings("unchecked")
public void accept(CompositeRecordReader.JoinCollector i, K key)
throws IOException, InterruptedException {
vjoin.clear();
if (key() != null && 0 == cmp.compare(key, key())) {
do {
vjoin.add(value);
} while (next() && 0 == cmp.compare(key, key()));
}
i.add(id, vjoin);
}
/**
* Read the next k,v pair into the head of this object; return true iff
* the RR and this are exhausted.
*/
public boolean nextKeyValue() throws IOException, InterruptedException {
if (hasNext()) {
next();
return true;
}
return false;
}
/**
* Read the next k,v pair into the head of this object; return true iff
* the RR and this are exhausted.
*/
private boolean next() throws IOException, InterruptedException {
empty = !rr.nextKeyValue();
key = rr.getCurrentKey();
value = rr.getCurrentValue();
return !empty;
}
/**
* Get current key
*/
public K getCurrentKey() throws IOException, InterruptedException {
return rr.getCurrentKey();
}
/**
* Get current value
*/
public U getCurrentValue() throws IOException, InterruptedException {
return rr.getCurrentValue();
}
/**
* Request progress from proxied RR.
*/
public float getProgress() throws IOException, InterruptedException {
return rr.getProgress();
}
/**
* Forward close request to proxied RR.
*/
public void close() throws IOException {
rr.close();
}
/**
* Implement Comparable contract (compare key at head of proxied RR
* with that of another).
*/
public int compareTo(ComposableRecordReader<K,?> other) {
return cmp.compare(key(), other.key());
}
/**
* Return true iff compareTo(other) retn true.
*/
@SuppressWarnings("unchecked") // Explicit type check prior to cast
public boolean equals(Object other) {
return other instanceof ComposableRecordReader
&& 0 == compareTo((ComposableRecordReader)other);
}
public int hashCode() {
assert false : "hashCode not designed";
return 42;
}
}