/**
* 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.lib.join;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import org.apache.avro.io.BinaryEncoder;
import org.apache.avro.io.EncoderFactory;
import org.apache.avro.reflect.ReflectDatumWriter;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.crunch.CrunchRuntimeException;
import org.apache.crunch.DoFn;
import org.apache.crunch.Emitter;
import org.apache.crunch.FilterFn;
import org.apache.crunch.MapFn;
import org.apache.crunch.PCollection;
import org.apache.crunch.PTable;
import org.apache.crunch.Pair;
import org.apache.crunch.ParallelDoOptions;
import org.apache.crunch.ReadableData;
import org.apache.crunch.impl.mr.MRPipeline;
import org.apache.crunch.types.PType;
import org.apache.crunch.types.PTypeFamily;
import org.apache.crunch.types.avro.AvroType;
import org.apache.crunch.types.avro.AvroTypeFamily;
import org.apache.crunch.types.avro.Avros;
import org.apache.crunch.types.writable.WritableType;
import org.apache.crunch.types.writable.WritableTypeFamily;
import org.apache.crunch.types.writable.Writables;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.DataOutputBuffer;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.util.bloom.BloomFilter;
import org.apache.hadoop.util.bloom.Key;
import org.apache.hadoop.util.hash.Hash;
/**
* Join strategy that uses a <a href="http://en.wikipedia.org/wiki/Bloom_filter">Bloom filter</a>
* that is trained on the keys of the left-side table to filter the key/value pairs of the right-side
* table before sending through the shuffle and reduce phase.
* <p>
* This strategy is useful in cases where the right-side table contains many keys that are not
* present in the left-side table. In this case, the use of the Bloom filter avoids a
* potentially costly shuffle phase for data that would never be joined to the left side.
*/
public class BloomFilterJoinStrategy<K, U, V> implements JoinStrategy<K, U, V> {
private static final Log LOG = LogFactory.getLog(BloomFilterJoinStrategy.class);
private int vectorSize;
private int nbHash;
private JoinStrategy<K, U, V> delegateJoinStrategy;
/**
* Instantiate with the expected number of unique keys in the left table.
* <p>
* The {@link DefaultJoinStrategy} will be used to perform the actual join after filtering.
*
* @param numElements expected number of unique keys
*/
public BloomFilterJoinStrategy(int numElements) {
this(numElements, 0.05f);
}
/**
* Instantiate with the expected number of unique keys in the left table, and the acceptable
* false positive rate for the Bloom filter.
* <p>
* The {@link DefaultJoinStrategy} will be used to perform the actual join after filtering.
*
* @param numElements expected number of unique keys
* @param falsePositiveRate acceptable false positive rate for Bloom Filter
*/
public BloomFilterJoinStrategy(int numElements, float falsePositiveRate) {
this(numElements, falsePositiveRate, new DefaultJoinStrategy<K, U, V>());
}
/**
* Instantiate with the expected number of unique keys in the left table, and the acceptable
* false positive rate for the Bloom filter, and an underlying join strategy to delegate to.
*
* @param numElements expected number of unique keys
* @param falsePositiveRate acceptable false positive rate for Bloom Filter
* @param delegateJoinStrategy join strategy to delegate to after filtering
*/
public BloomFilterJoinStrategy(int numElements, float falsePositiveRate, JoinStrategy<K,U,V> delegateJoinStrategy) {
this.vectorSize = getOptimalVectorSize(numElements, falsePositiveRate);
this.nbHash = getOptimalNumHash(numElements, vectorSize);
this.delegateJoinStrategy = delegateJoinStrategy;
}
/**
* Calculates the optimal vector size for a given number of elements and acceptable false
* positive rate.
*/
private static int getOptimalVectorSize(int numElements, float falsePositiveRate) {
return (int) (-numElements * (float)Math.log(falsePositiveRate) / Math.pow(Math.log(2), 2));
}
/**
* Calculates the optimal number of hash functions to be used.
*/
private static int getOptimalNumHash(int numElements, float vectorSize) {
return (int)Math.round(vectorSize * Math.log(2) / numElements);
}
@Override
public PTable<K, Pair<U, V>> join(PTable<K, U> left, PTable<K, V> right, JoinType joinType) {
if (joinType != JoinType.INNER_JOIN && joinType != JoinType.LEFT_OUTER_JOIN) {
throw new IllegalStateException("JoinType " + joinType + " is not supported for BloomFilter joins");
}
PTable<K,V> filteredRightSide;
PType<BloomFilter> bloomFilterType = getBloomFilterType(left.getTypeFamily());
PCollection<BloomFilter> bloomFilters = left.keys().parallelDo(
"Create bloom filters",
new CreateBloomFilterFn(vectorSize, nbHash, left.getKeyType()),
bloomFilterType);
ReadableData<BloomFilter> bloomData = bloomFilters.asReadable(true);
FilterKeysWithBloomFilterFn<K, V> filterKeysFn = new FilterKeysWithBloomFilterFn<K, V>(
bloomData,
vectorSize, nbHash,
left.getKeyType());
ParallelDoOptions.Builder optionsBuilder = ParallelDoOptions.builder();
optionsBuilder.sourceTargets(bloomData.getSourceTargets());
filteredRightSide = right.parallelDo("Filter right side with BloomFilters",
filterKeysFn, right.getPTableType(), optionsBuilder.build());
return delegateJoinStrategy.join(left, filteredRightSide, joinType);
}
/**
* Creates Bloom filter(s) for filtering of right-side keys.
*/
private static class CreateBloomFilterFn<K> extends DoFn<K, BloomFilter> {
private int vectorSize;
private int nbHash;
private transient BloomFilter bloomFilter;
private transient MapFn<K,byte[]> keyToBytesFn;
private PType<K> ptype;
CreateBloomFilterFn(int vectorSize, int nbHash, PType<K> ptype) {
this.vectorSize = vectorSize;
this.nbHash = nbHash;
this.ptype = ptype;
}
@Override
public void initialize() {
super.initialize();
bloomFilter = new BloomFilter(vectorSize, nbHash, Hash.MURMUR_HASH);
ptype.initialize(getConfiguration());
keyToBytesFn = getKeyToBytesMapFn(ptype, getConfiguration());
}
@Override
public void process(K input, Emitter<BloomFilter> emitter) {
bloomFilter.add(new Key(keyToBytesFn.map(input)));
}
@Override
public void cleanup(Emitter<BloomFilter> emitter) {
emitter.emit(bloomFilter);
}
}
/**
* Filters right-side keys with a Bloom filter before passing them off to the delegate join strategy.
*/
private static class FilterKeysWithBloomFilterFn<K,V> extends FilterFn<Pair<K, V>> {
private int vectorSize;
private int nbHash;
private PType<K> keyType;
private PType<BloomFilter> bloomFilterPType;
private BloomFilter bloomFilter;
private transient MapFn<K,byte[]> keyToBytesFn;
private ReadableData<BloomFilter> bloomData;
FilterKeysWithBloomFilterFn(ReadableData<BloomFilter> bloomData, int vectorSize, int nbHash, PType<K> keyType) {
this.bloomData = bloomData;
this.vectorSize = vectorSize;
this.nbHash = nbHash;
this.keyType = keyType;
}
@Override
public void configure(Configuration conf) {
bloomData.configure(conf);
}
@Override
public void initialize() {
super.initialize();
keyType.initialize(getConfiguration());
keyToBytesFn = getKeyToBytesMapFn(keyType, getConfiguration());
Iterable<BloomFilter> iterable;
try {
iterable = bloomData.read(getContext());
} catch (IOException e) {
throw new CrunchRuntimeException("Error reading right-side of map side join: ", e);
}
bloomFilter = new BloomFilter(vectorSize, nbHash, Hash.MURMUR_HASH);
for (BloomFilter subFilter : iterable) {
bloomFilter.or(subFilter);
}
}
@Override
public boolean accept(Pair<K, V> input) {
Key key = new Key(keyToBytesFn.map(input.first()));
return bloomFilter.membershipTest(key);
}
}
/**
* Returns the appropriate MapFn for converting the key type into byte arrays.
*/
private static <K> MapFn<K,byte[]> getKeyToBytesMapFn(PType<K> ptype, Configuration conf) {
if (ptype instanceof AvroType) {
return new AvroToBytesFn<K>((AvroType)ptype, conf);
}
if (ptype instanceof WritableType) {
return new WritableToBytesFn<K>((WritableType)ptype, conf);
}
throw new IllegalStateException("Unrecognized PType: " + ptype);
}
/**
* Returns the appropriate PType for serializing BloomFilters using the same
* type family as is used for the input collections.
*/
private static PType<BloomFilter> getBloomFilterType(PTypeFamily typeFamily) {
if (typeFamily.equals(AvroTypeFamily.getInstance())) {
return Avros.writables(BloomFilter.class);
} else if (typeFamily.equals(WritableTypeFamily.getInstance())) {
return Writables.writables(BloomFilter.class);
} else {
throw new IllegalStateException("Unrecognized PTypeFamily: " + typeFamily);
}
}
/**
* Converts a Writable into a byte array so that it can be added to a BloomFilter.
*/
private static class WritableToBytesFn<T> extends MapFn<T,byte[]>{
private WritableType<T,?> ptype;
private DataOutputBuffer dataOutputBuffer;
WritableToBytesFn(WritableType<T,?> ptype, Configuration conf) {
this.ptype = ptype;
dataOutputBuffer = new DataOutputBuffer();
}
@Override
public byte[] map(T input) {
dataOutputBuffer.reset();
Writable writable = (Writable) ptype.getOutputMapFn().map(input);
try {
writable.write(dataOutputBuffer);
} catch (IOException e) {
throw new CrunchRuntimeException(e);
}
byte[] output = new byte[dataOutputBuffer.getLength()];
System.arraycopy(dataOutputBuffer.getData(), 0, output, 0, dataOutputBuffer.getLength());
return output;
}
}
/**
* Converts an Avro value into a byte array so that it can be added to a Bloom filter.
*/
private static class AvroToBytesFn<T> extends MapFn<T,byte[]> {
private AvroType<T> ptype;
private BinaryEncoder encoder;
private ReflectDatumWriter datumWriter;
AvroToBytesFn(AvroType<T> ptype, Configuration conf) {
this.ptype = ptype;
datumWriter = Avros.getReflectDataFactory(conf).getWriter(ptype.getSchema());
}
@Override
public byte[] map(T input) {
Object datum = ptype.getOutputMapFn().map(input);
ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
encoder = EncoderFactory.get().binaryEncoder(byteArrayOutputStream, encoder);
try {
datumWriter.write(datum, encoder);
encoder.flush();
} catch (IOException e) {
throw new CrunchRuntimeException(e);
}
return byteArrayOutputStream.toByteArray();
}
}
}