/*
* 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.flink.runtime.operators.hash;
import java.io.EOFException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.flink.api.common.typeutils.TypeComparator;
import org.apache.flink.api.common.typeutils.TypePairComparator;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.core.memory.MemorySegment;
import org.apache.flink.runtime.memory.ListMemorySegmentSource;
import org.apache.flink.runtime.util.IntArrayList;
import org.apache.flink.runtime.util.LongArrayList;
import org.apache.flink.util.MathUtils;
import org.apache.flink.util.MutableObjectIterator;
/**
* A hash table that uses Flink's managed memory and supports replacement of records or
* updates to records. For an overview of the general data structure of the hash table, please
* refer to the description of the {@link org.apache.flink.runtime.operators.hash.MutableHashTable}.
*
* <p>The hash table is internally divided into two parts: The hash index, and the partition buffers
* that store the actual records. When records are inserted or updated, the hash table appends the
* records to its corresponding partition, and inserts or updates the entry in the hash index.
* In the case that the hash table runs out of memory, it compacts a partition by walking through the
* hash index and copying all reachable elements into a fresh partition. After that, it releases the
* memory of the partition to compact.</p>
*
* @param <T> Record type stored in hash table
*/
public class CompactingHashTable<T> extends AbstractMutableHashTable<T> {
private static final Logger LOG = LoggerFactory.getLogger(CompactingHashTable.class);
// ------------------------------------------------------------------------
// Internal Constants
// ------------------------------------------------------------------------
/** The minimum number of memory segments that the compacting hash table needs to work properly */
private static final int MIN_NUM_MEMORY_SEGMENTS = 33;
/** The maximum number of partitions */
private static final int MAX_NUM_PARTITIONS = 32;
/**
* The default record width that is used when no width is given. The record width is
* used to determine the ratio of the number of memory segments intended for partition
* buffers and the number of memory segments in the hash-table structure.
*/
private static final int DEFAULT_RECORD_LEN = 24;
/**
* The length of the hash code stored in the bucket.
*/
private static final int HASH_CODE_LEN = 4;
/**
* The length of a pointer from a hash bucket to the record in the buffers.
*/
private static final int POINTER_LEN = 8;
/**
* The number of bytes that the entry in the hash structure occupies, in bytes.
* It corresponds to a 4 byte hash value and an 8 byte pointer.
*/
private static final int RECORD_TABLE_BYTES = HASH_CODE_LEN + POINTER_LEN;
/**
* The total storage overhead per record, in bytes. This corresponds to the space in the
* actual hash table buckets, consisting of a 4 byte hash value and an 8 byte
* pointer, plus the overhead for the stored length field.
*/
private static final int RECORD_OVERHEAD_BYTES = RECORD_TABLE_BYTES + 2;
// -------------------------- Bucket Size and Structure -------------------------------------
private static final int NUM_INTRA_BUCKET_BITS = 7;
private static final int HASH_BUCKET_SIZE = 0x1 << NUM_INTRA_BUCKET_BITS;
private static final int BUCKET_HEADER_LENGTH = 16;
private static final int NUM_ENTRIES_PER_BUCKET = (HASH_BUCKET_SIZE - BUCKET_HEADER_LENGTH) / RECORD_TABLE_BYTES;
private static final int BUCKET_POINTER_START_OFFSET = BUCKET_HEADER_LENGTH + (NUM_ENTRIES_PER_BUCKET * HASH_CODE_LEN);
// ------------------------------ Bucket Header Fields ------------------------------
/**
* Offset of the field in the bucket header indicating the bucket's partition.
*/
private static final int HEADER_PARTITION_OFFSET = 0;
/**
* Offset of the field in the bucket header indicating the bucket's status (spilled or in-memory).
*/
private static final int HEADER_COUNT_OFFSET = 4;
/**
* Offset of the field in the bucket header that holds the forward pointer to its
* first overflow bucket.
*/
private static final int HEADER_FORWARD_OFFSET = 8;
/**
* Constant for the forward pointer, indicating that the pointer is not set.
*/
private static final long BUCKET_FORWARD_POINTER_NOT_SET = ~0x0L;
// ------------------------------------------------------------------------
// Members
// ------------------------------------------------------------------------
/** The free memory segments currently available to the hash join. */
private final ArrayList<MemorySegment> availableMemory;
/** The size of the segments used by the hash join buckets.
* All segments must be of equal size to ease offset computations. */
private final int segmentSize;
/**
* The number of hash table buckets in a single memory segment - 1.
* Because memory segments can be comparatively large, we fit multiple buckets into one memory segment.
* This variable is a mask that is 1 in the lower bits that define the number of a bucket
* in a segment.
*/
private final int bucketsPerSegmentMask;
/** The number of bits that describe the position of a bucket in a memory segment.
* Computed as log2(bucketsPerSegment). */
private final int bucketsPerSegmentBits;
/** An estimate for the average record length. */
private final int avgRecordLen;
private final int pageSizeInBits;
// ------------------------------------------------------------------------
/** The partitions of the hash table. */
private final ArrayList<InMemoryPartition<T>> partitions;
/** The array of memory segments that contain the buckets which form the actual hash-table
* of hash-codes and pointers to the elements. */
private MemorySegment[] buckets;
/** Temporary storage for partition compaction (always attempts to allocate
* as many segments as the largest partition) */
private InMemoryPartition<T> compactionMemory;
/** The number of buckets in the current table. The bucket array is not necessarily fully
* used, when not all buckets that would fit into the last segment are actually used. */
private int numBuckets;
/** Flag to interrupt closed loops */
private boolean running = true;
/** Flag necessary so a resize is never triggered during a resize since the code paths are interleaved */
private boolean isResizing;
// ------------------------------------------------------------------------
// Construction and Teardown
// ------------------------------------------------------------------------
public CompactingHashTable(TypeSerializer<T> buildSideSerializer,
TypeComparator<T> buildSideComparator,
List<MemorySegment> memorySegments) {
this(buildSideSerializer, buildSideComparator, memorySegments, DEFAULT_RECORD_LEN);
}
public CompactingHashTable(TypeSerializer<T> buildSideSerializer,
TypeComparator<T> buildSideComparator,
List<MemorySegment> memorySegments,
int avgRecordLen) {
super(buildSideSerializer, buildSideComparator);
// some sanity checks first
if (memorySegments == null) {
throw new NullPointerException();
}
if (memorySegments.size() < MIN_NUM_MEMORY_SEGMENTS) {
throw new IllegalArgumentException("Too few memory segments provided. Hash Table needs at least " +
MIN_NUM_MEMORY_SEGMENTS + " memory segments.");
}
this.availableMemory = (memorySegments instanceof ArrayList) ?
(ArrayList<MemorySegment>) memorySegments :
new ArrayList<MemorySegment>(memorySegments);
this.avgRecordLen = buildSideSerializer.getLength() > 0 ? buildSideSerializer.getLength() : avgRecordLen;
// check the size of the first buffer and record it. all further buffers must have the same size.
// the size must also be a power of 2
this.segmentSize = memorySegments.get(0).size();
if ( (this.segmentSize & this.segmentSize - 1) != 0) {
throw new IllegalArgumentException("Hash Table requires buffers whose size is a power of 2.");
}
this.pageSizeInBits = MathUtils.log2strict(this.segmentSize);
int bucketsPerSegment = this.segmentSize >> NUM_INTRA_BUCKET_BITS;
if (bucketsPerSegment == 0) {
throw new IllegalArgumentException("Hash Table requires buffers of at least " + HASH_BUCKET_SIZE + " bytes.");
}
this.bucketsPerSegmentMask = bucketsPerSegment - 1;
this.bucketsPerSegmentBits = MathUtils.log2strict(bucketsPerSegment);
this.partitions = new ArrayList<InMemoryPartition<T>>();
// so far no partition has any MemorySegments
}
// ------------------------------------------------------------------------
// life cycle
// ------------------------------------------------------------------------
/**
* Initialize the hash table
*/
@Override
public void open() {
synchronized (stateLock) {
if (!closed) {
throw new IllegalStateException("currently not closed.");
}
closed = false;
}
// create the partitions
final int partitionFanOut = getPartitioningFanOutNoEstimates(this.availableMemory.size());
createPartitions(partitionFanOut);
// set up the table structure. the write behind buffers are taken away, as are one buffer per partition
final int numBuckets = getInitialTableSize(this.availableMemory.size(), this.segmentSize,
partitionFanOut, this.avgRecordLen);
initTable(numBuckets, (byte) partitionFanOut);
}
/**
* Closes the hash table. This effectively releases all internal structures and closes all
* open files and removes them. The call to this method is valid both as a cleanup after the
* complete inputs were properly processed, and as an cancellation call, which cleans up
* all resources that are currently held by the hash join. If another process still access the hash
* table after close has been called no operations will be performed.
*/
@Override
public void close() {
// make sure that we close only once
synchronized (this.stateLock) {
if (this.closed) {
return;
}
this.closed = true;
}
LOG.debug("Closing hash table and releasing resources.");
// release the table structure
releaseTable();
// clear the memory in the partitions
clearPartitions();
}
@Override
public void abort() {
this.running = false;
LOG.debug("Cancelling hash table operations.");
}
@Override
public List<MemorySegment> getFreeMemory() {
if (!this.closed) {
throw new IllegalStateException("Cannot return memory while join is open.");
}
return this.availableMemory;
}
// ------------------------------------------------------------------------
// adding data to the hash table
// ------------------------------------------------------------------------
public void buildTableWithUniqueKey(final MutableObjectIterator<T> input) throws IOException {
// go over the complete input and insert every element into the hash table
T value;
while (this.running && (value = input.next()) != null) {
insertOrReplaceRecord(value);
}
}
@Override
public final void insert(T record) throws IOException {
if (this.closed) {
return;
}
final int hashCode = MathUtils.jenkinsHash(this.buildSideComparator.hash(record));
final int posHashCode = hashCode % this.numBuckets;
// get the bucket for the given hash code
final int bucketArrayPos = posHashCode >>> this.bucketsPerSegmentBits;
final int bucketInSegmentPos = (posHashCode & this.bucketsPerSegmentMask) << NUM_INTRA_BUCKET_BITS;
final MemorySegment bucket = this.buckets[bucketArrayPos];
// get the basic characteristics of the bucket
final int partitionNumber = bucket.get(bucketInSegmentPos + HEADER_PARTITION_OFFSET);
InMemoryPartition<T> partition = this.partitions.get(partitionNumber);
long pointer = insertRecordIntoPartition(record, partition, false);
insertBucketEntryFromStart(bucket, bucketInSegmentPos, hashCode, pointer, partitionNumber);
}
/**
* Replaces record in hash table if record already present or append record if not.
* May trigger expensive compaction.
*
* @param record record to insert or replace
* @throws IOException
*/
public void insertOrReplaceRecord(T record) throws IOException {
if (this.closed) {
return;
}
final int searchHashCode = MathUtils.jenkinsHash(this.buildSideComparator.hash(record));
final int posHashCode = searchHashCode % this.numBuckets;
// get the bucket for the given hash code
final MemorySegment originalBucket = this.buckets[posHashCode >> this.bucketsPerSegmentBits];
final int originalBucketOffset = (posHashCode & this.bucketsPerSegmentMask) << NUM_INTRA_BUCKET_BITS;
MemorySegment bucket = originalBucket;
int bucketInSegmentOffset = originalBucketOffset;
// get the basic characteristics of the bucket
final int partitionNumber = bucket.get(bucketInSegmentOffset + HEADER_PARTITION_OFFSET);
final InMemoryPartition<T> partition = this.partitions.get(partitionNumber);
final MemorySegment[] overflowSegments = partition.overflowSegments;
this.buildSideComparator.setReference(record);
int countInSegment = bucket.getInt(bucketInSegmentOffset + HEADER_COUNT_OFFSET);
int numInSegment = 0;
int posInSegment = bucketInSegmentOffset + BUCKET_HEADER_LENGTH;
// loop over all segments that are involved in the bucket (original bucket plus overflow buckets)
while (true) {
while (numInSegment < countInSegment) {
final int thisCode = bucket.getInt(posInSegment);
posInSegment += HASH_CODE_LEN;
// check if the hash code matches
if (thisCode == searchHashCode) {
// get the pointer to the pair
final int pointerOffset = bucketInSegmentOffset + BUCKET_POINTER_START_OFFSET + (numInSegment * POINTER_LEN);
final long pointer = bucket.getLong(pointerOffset);
// deserialize the key to check whether it is really equal, or whether we had only a hash collision
T valueAtPosition = partition.readRecordAt(pointer);
if (this.buildSideComparator.equalToReference(valueAtPosition)) {
long newPointer = insertRecordIntoPartition(record, partition, true);
bucket.putLong(pointerOffset, newPointer);
return;
}
}
numInSegment++;
}
// this segment is done. check if there is another chained bucket
long newForwardPointer = bucket.getLong(bucketInSegmentOffset + HEADER_FORWARD_OFFSET);
if (newForwardPointer == BUCKET_FORWARD_POINTER_NOT_SET) {
// nothing found. append and insert
long pointer = insertRecordIntoPartition(record, partition, false);
if (countInSegment < NUM_ENTRIES_PER_BUCKET) {
// we are good in our current bucket, put the values
bucket.putInt(bucketInSegmentOffset + BUCKET_HEADER_LENGTH + (countInSegment * HASH_CODE_LEN), searchHashCode); // hash code
bucket.putLong(bucketInSegmentOffset + BUCKET_POINTER_START_OFFSET + (countInSegment * POINTER_LEN), pointer); // pointer
bucket.putInt(bucketInSegmentOffset + HEADER_COUNT_OFFSET, countInSegment + 1); // update count
}
else {
insertBucketEntryFromStart(originalBucket, originalBucketOffset, searchHashCode, pointer, partitionNumber);
}
return;
}
final int overflowSegNum = (int) (newForwardPointer >>> 32);
bucket = overflowSegments[overflowSegNum];
bucketInSegmentOffset = (int) newForwardPointer;
countInSegment = bucket.getInt(bucketInSegmentOffset + HEADER_COUNT_OFFSET);
posInSegment = bucketInSegmentOffset + BUCKET_HEADER_LENGTH;
numInSegment = 0;
}
}
private long insertRecordIntoPartition(T record, InMemoryPartition<T> partition,
boolean fragments) throws IOException {
try {
long pointer = partition.appendRecord(record);
if (fragments) {
partition.setIsCompacted(false);
}
if ((pointer >> this.pageSizeInBits) > this.compactionMemory.getBlockCount()) {
this.compactionMemory.allocateSegments((int)(pointer >> this.pageSizeInBits));
}
return pointer;
}
catch (Exception e) {
if (e instanceof EOFException || e instanceof IndexOutOfBoundsException) {
// this indicates an out of memory situation
try {
final int partitionNumber = partition.getPartitionNumber();
compactPartition(partitionNumber);
// retry append
partition = this.partitions.get(partitionNumber); // compaction invalidates reference
long newPointer = partition.appendRecord(record);
if ((newPointer >> this.pageSizeInBits) > this.compactionMemory.getBlockCount()) {
this.compactionMemory.allocateSegments((int)(newPointer >> this.pageSizeInBits));
}
return newPointer;
}
catch (EOFException | IndexOutOfBoundsException ex) {
throw new RuntimeException("Memory ran out. Compaction failed. " +
getMemoryConsumptionString() + " Message: " + ex.getMessage());
}
}
else if (e instanceof IOException) {
throw (IOException) e;
}
else //noinspection ConstantConditions
if (e instanceof RuntimeException) {
throw (RuntimeException) e;
}
else {
throw new RuntimeException("Writing record to compacting hash table failed", e);
}
}
}
/**
* IMPORTANT!!! We pass only the partition number, because we must make sure we get a fresh
* partition reference. The partition reference used during search for the key may have become
* invalid during the compaction.
*/
private void insertBucketEntryFromStart(MemorySegment bucket, int bucketInSegmentPos,
int hashCode, long pointer, int partitionNumber)
throws IOException
{
boolean checkForResize = false;
// find the position to put the hash code and pointer
final int count = bucket.getInt(bucketInSegmentPos + HEADER_COUNT_OFFSET);
if (count < NUM_ENTRIES_PER_BUCKET) {
// we are good in our current bucket, put the values
bucket.putInt(bucketInSegmentPos + BUCKET_HEADER_LENGTH + (count * HASH_CODE_LEN), hashCode); // hash code
bucket.putLong(bucketInSegmentPos + BUCKET_POINTER_START_OFFSET + (count * POINTER_LEN), pointer); // pointer
bucket.putInt(bucketInSegmentPos + HEADER_COUNT_OFFSET, count + 1); // update count
}
else {
// we need to go to the overflow buckets
final InMemoryPartition<T> p = this.partitions.get(partitionNumber);
final long originalForwardPointer = bucket.getLong(bucketInSegmentPos + HEADER_FORWARD_OFFSET);
final long forwardForNewBucket;
if (originalForwardPointer != BUCKET_FORWARD_POINTER_NOT_SET) {
// forward pointer set
final int overflowSegNum = (int) (originalForwardPointer >>> 32);
final int segOffset = (int) originalForwardPointer;
final MemorySegment seg = p.overflowSegments[overflowSegNum];
final int obCount = seg.getInt(segOffset + HEADER_COUNT_OFFSET);
// check if there is space in this overflow bucket
if (obCount < NUM_ENTRIES_PER_BUCKET) {
// space in this bucket and we are done
seg.putInt(segOffset + BUCKET_HEADER_LENGTH + (obCount * HASH_CODE_LEN), hashCode); // hash code
seg.putLong(segOffset + BUCKET_POINTER_START_OFFSET + (obCount * POINTER_LEN), pointer); // pointer
seg.putInt(segOffset + HEADER_COUNT_OFFSET, obCount + 1); // update count
return;
} else {
// no space here, we need a new bucket. this current overflow bucket will be the
// target of the new overflow bucket
forwardForNewBucket = originalForwardPointer;
}
} else {
// no overflow bucket yet, so we need a first one
forwardForNewBucket = BUCKET_FORWARD_POINTER_NOT_SET;
}
// we need a new overflow bucket
MemorySegment overflowSeg;
final int overflowBucketNum;
final int overflowBucketOffset;
// first, see if there is space for an overflow bucket remaining in the last overflow segment
if (p.nextOverflowBucket == 0) {
// no space left in last bucket, or no bucket yet, so create an overflow segment
overflowSeg = getNextBuffer();
overflowBucketOffset = 0;
overflowBucketNum = p.numOverflowSegments;
// add the new overflow segment
if (p.overflowSegments.length <= p.numOverflowSegments) {
MemorySegment[] newSegsArray = new MemorySegment[p.overflowSegments.length * 2];
System.arraycopy(p.overflowSegments, 0, newSegsArray, 0, p.overflowSegments.length);
p.overflowSegments = newSegsArray;
}
p.overflowSegments[p.numOverflowSegments] = overflowSeg;
p.numOverflowSegments++;
checkForResize = true;
} else {
// there is space in the last overflow bucket
overflowBucketNum = p.numOverflowSegments - 1;
overflowSeg = p.overflowSegments[overflowBucketNum];
overflowBucketOffset = p.nextOverflowBucket << NUM_INTRA_BUCKET_BITS;
}
// next overflow bucket is one ahead. if the segment is full, the next will be at the beginning
// of a new segment
p.nextOverflowBucket = (p.nextOverflowBucket == this.bucketsPerSegmentMask ? 0 : p.nextOverflowBucket + 1);
// insert the new overflow bucket in the chain of buckets
// 1) set the old forward pointer
// 2) let the bucket in the main table point to this one
overflowSeg.putLong(overflowBucketOffset + HEADER_FORWARD_OFFSET, forwardForNewBucket);
final long pointerToNewBucket = (((long) overflowBucketNum) << 32) | ((long) overflowBucketOffset);
bucket.putLong(bucketInSegmentPos + HEADER_FORWARD_OFFSET, pointerToNewBucket);
// finally, insert the values into the overflow buckets
overflowSeg.putInt(overflowBucketOffset + BUCKET_HEADER_LENGTH, hashCode); // hash code
overflowSeg.putLong(overflowBucketOffset + BUCKET_POINTER_START_OFFSET, pointer); // pointer
// set the count to one
overflowSeg.putInt(overflowBucketOffset + HEADER_COUNT_OFFSET, 1);
if (checkForResize && !this.isResizing) {
// check if we should resize buckets
if (this.buckets.length <= getOverflowSegmentCount()) {
resizeHashTable();
}
}
}
}
/**
* IMPORTANT!!! We pass only the partition number, because we must make sure we get a fresh
* partition reference. The partition reference used during search for the key may have become
* invalid during the compaction.
*/
private void insertBucketEntryFromSearch(MemorySegment originalBucket, MemorySegment currentBucket,
int originalBucketOffset, int currentBucketOffset,
int countInCurrentBucket, long originalForwardPointer,
int hashCode, long pointer, int partitionNumber) throws IOException {
boolean checkForResize = false;
if (countInCurrentBucket < NUM_ENTRIES_PER_BUCKET) {
// we are good in our current bucket, put the values
currentBucket.putInt(currentBucketOffset + BUCKET_HEADER_LENGTH + (countInCurrentBucket * HASH_CODE_LEN), hashCode); // hash code
currentBucket.putLong(currentBucketOffset + BUCKET_POINTER_START_OFFSET + (countInCurrentBucket * POINTER_LEN), pointer); // pointer
currentBucket.putInt(currentBucketOffset + HEADER_COUNT_OFFSET, countInCurrentBucket + 1); // update count
}
else {
// we go to a new overflow bucket
final InMemoryPartition<T> partition = this.partitions.get(partitionNumber);
MemorySegment overflowSeg;
final int overflowSegmentNum;
final int overflowBucketOffset;
// first, see if there is space for an overflow bucket remaining in the last overflow segment
if (partition.nextOverflowBucket == 0) {
// no space left in last bucket, or no bucket yet, so create an overflow segment
overflowSeg = getNextBuffer();
overflowBucketOffset = 0;
overflowSegmentNum = partition.numOverflowSegments;
// add the new overflow segment
if (partition.overflowSegments.length <= partition.numOverflowSegments) {
MemorySegment[] newSegsArray = new MemorySegment[partition.overflowSegments.length * 2];
System.arraycopy(partition.overflowSegments, 0, newSegsArray, 0, partition.overflowSegments.length);
partition.overflowSegments = newSegsArray;
}
partition.overflowSegments[partition.numOverflowSegments] = overflowSeg;
partition.numOverflowSegments++;
checkForResize = true;
}
else {
// there is space in the last overflow segment
overflowSegmentNum = partition.numOverflowSegments - 1;
overflowSeg = partition.overflowSegments[overflowSegmentNum];
overflowBucketOffset = partition.nextOverflowBucket << NUM_INTRA_BUCKET_BITS;
}
// next overflow bucket is one ahead. if the segment is full, the next will be at the beginning
// of a new segment
partition.nextOverflowBucket = (partition.nextOverflowBucket == this.bucketsPerSegmentMask ? 0 : partition.nextOverflowBucket + 1);
// insert the new overflow bucket in the chain of buckets
// 1) set the old forward pointer
// 2) let the bucket in the main table point to this one
overflowSeg.putLong(overflowBucketOffset + HEADER_FORWARD_OFFSET, originalForwardPointer);
final long pointerToNewBucket = (((long) overflowSegmentNum) << 32) | ((long) overflowBucketOffset);
originalBucket.putLong(originalBucketOffset + HEADER_FORWARD_OFFSET, pointerToNewBucket);
// finally, insert the values into the overflow buckets
overflowSeg.putInt(overflowBucketOffset + BUCKET_HEADER_LENGTH, hashCode); // hash code
overflowSeg.putLong(overflowBucketOffset + BUCKET_POINTER_START_OFFSET, pointer); // pointer
// set the count to one
overflowSeg.putInt(overflowBucketOffset + HEADER_COUNT_OFFSET, 1);
if(checkForResize && !this.isResizing) {
// check if we should resize buckets
if(this.buckets.length <= getOverflowSegmentCount()) {
resizeHashTable();
}
}
}
}
// --------------------------------------------------------------------------------------------
// Access to the entries
// --------------------------------------------------------------------------------------------
@Override
public <PT> HashTableProber<PT> getProber(TypeComparator<PT> probeSideComparator, TypePairComparator<PT, T> pairComparator) {
return new HashTableProber<PT>(probeSideComparator, pairComparator);
}
/**
*
* @return Iterator over hash table
* @see EntryIterator
*/
public MutableObjectIterator<T> getEntryIterator() {
return new EntryIterator(this);
}
// --------------------------------------------------------------------------------------------
// Setup and Tear Down of Structures
// --------------------------------------------------------------------------------------------
private void createPartitions(int numPartitions) {
this.partitions.clear();
ListMemorySegmentSource memSource = new ListMemorySegmentSource(this.availableMemory);
for (int i = 0; i < numPartitions; i++) {
this.partitions.add(new InMemoryPartition<T>(this.buildSideSerializer, i, memSource, this.segmentSize, pageSizeInBits));
}
this.compactionMemory = new InMemoryPartition<T>(this.buildSideSerializer, -1, memSource, this.segmentSize, pageSizeInBits);
}
private void clearPartitions() {
for (InMemoryPartition<T> p : this.partitions) {
p.clearAllMemory(this.availableMemory);
}
this.partitions.clear();
this.compactionMemory.clearAllMemory(availableMemory);
}
private void initTable(int numBuckets, byte numPartitions) {
final int bucketsPerSegment = this.bucketsPerSegmentMask + 1;
final int numSegs = (numBuckets >>> this.bucketsPerSegmentBits) + ( (numBuckets & this.bucketsPerSegmentMask) == 0 ? 0 : 1);
final MemorySegment[] table = new MemorySegment[numSegs];
// go over all segments that are part of the table
for (int i = 0, bucket = 0; i < numSegs && bucket < numBuckets; i++) {
final MemorySegment seg = getNextBuffer();
// go over all buckets in the segment
for (int k = 0; k < bucketsPerSegment && bucket < numBuckets; k++, bucket++) {
final int bucketOffset = k * HASH_BUCKET_SIZE;
// compute the partition that the bucket corresponds to
final byte partition = assignPartition(bucket, numPartitions);
// initialize the header fields
seg.put(bucketOffset + HEADER_PARTITION_OFFSET, partition);
seg.putInt(bucketOffset + HEADER_COUNT_OFFSET, 0);
seg.putLong(bucketOffset + HEADER_FORWARD_OFFSET, BUCKET_FORWARD_POINTER_NOT_SET);
}
table[i] = seg;
}
this.buckets = table;
this.numBuckets = numBuckets;
}
private void releaseTable() {
// set the counters back
this.numBuckets = 0;
if (this.buckets != null) {
for (MemorySegment bucket : this.buckets) {
this.availableMemory.add(bucket);
}
this.buckets = null;
}
}
private MemorySegment getNextBuffer() {
// check if the list directly offers memory
int s = this.availableMemory.size();
if (s > 0) {
return this.availableMemory.remove(s-1);
} else {
throw new RuntimeException("Memory ran out. " + getMemoryConsumptionString());
}
}
// --------------------------------------------------------------------------------------------
// Utility Computational Functions
// --------------------------------------------------------------------------------------------
/**
* Gets the number of partitions to be used for an initial hash-table, when no estimates are
* available.
* <p>
* The current logic makes sure that there are always between 10 and 32 partitions, and close
* to 0.1 of the number of buffers.
*
* @param numBuffers The number of buffers available.
* @return The number of partitions to use.
*/
private static int getPartitioningFanOutNoEstimates(int numBuffers) {
return Math.max(10, Math.min(numBuffers / 10, MAX_NUM_PARTITIONS));
}
/**
* @return String containing a summary of the memory consumption for error messages
*/
private String getMemoryConsumptionString() {
return "numPartitions: " + this.partitions.size() +
" minPartition: " + getMinPartition() +
" maxPartition: " + getMaxPartition() +
" number of overflow segments: " + getOverflowSegmentCount() +
" bucketSize: " + this.buckets.length +
" Overall memory: " + getSize() +
" Partition memory: " + getPartitionSize();
}
/**
* Size of all memory segments owned by this hash table
*
* @return size in bytes
*/
private long getSize() {
long numSegments = 0;
numSegments += this.availableMemory.size();
numSegments += this.buckets.length;
for(InMemoryPartition<T> p : this.partitions) {
numSegments += p.getBlockCount();
numSegments += p.numOverflowSegments;
}
numSegments += this.compactionMemory.getBlockCount();
return numSegments*this.segmentSize;
}
/**
* Size of all memory segments owned by the partitions of this hash table excluding the compaction partition
*
* @return size in bytes
*/
private long getPartitionSize() {
long numSegments = 0;
for(InMemoryPartition<T> p : this.partitions) {
numSegments += p.getBlockCount();
}
return numSegments*this.segmentSize;
}
/**
* @return number of memory segments in the largest partition
*/
private int getMaxPartition() {
int maxPartition = 0;
for(InMemoryPartition<T> p1 : this.partitions) {
if(p1.getBlockCount() > maxPartition) {
maxPartition = p1.getBlockCount();
}
}
return maxPartition;
}
/**
* @return number of memory segments in the smallest partition
*/
private int getMinPartition() {
int minPartition = Integer.MAX_VALUE;
for(InMemoryPartition<T> p1 : this.partitions) {
if(p1.getBlockCount() < minPartition) {
minPartition = p1.getBlockCount();
}
}
return minPartition;
}
/**
* @return number of memory segments used in overflow buckets
*/
private int getOverflowSegmentCount() {
int result = 0;
for (InMemoryPartition<T> p : this.partitions) {
result += p.numOverflowSegments;
}
return result;
}
/**
* tries to find a good value for the number of buckets
* will ensure that the number of buckets is a multiple of numPartitions
*
* @return number of buckets
*/
private static int getInitialTableSize(int numBuffers, int bufferSize, int numPartitions, int recordLenBytes) {
final long totalSize = ((long) bufferSize) * numBuffers;
final long numRecordsStorable = totalSize / (recordLenBytes + RECORD_OVERHEAD_BYTES);
final long bucketBytes = numRecordsStorable * RECORD_OVERHEAD_BYTES;
long numBuckets = bucketBytes / (2 * HASH_BUCKET_SIZE) + 1;
numBuckets += numPartitions - numBuckets % numPartitions;
return numBuckets > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int) numBuckets;
}
/**
* Assigns a partition to a bucket.
*
* @param bucket bucket index
* @param numPartitions number of partitions
* @return The hash code for the integer.
*/
private static byte assignPartition(int bucket, byte numPartitions) {
return (byte) (bucket % numPartitions);
}
/**
* Attempts to double the number of buckets
*
* @return true on success
* @throws IOException
*/
private boolean resizeHashTable() throws IOException {
final int newNumBuckets = 2*this.numBuckets;
final int bucketsPerSegment = this.bucketsPerSegmentMask + 1;
final int newNumSegments = (newNumBuckets + (bucketsPerSegment-1)) / bucketsPerSegment;
final int additionalSegments = newNumSegments-this.buckets.length;
final int numPartitions = this.partitions.size();
if (this.availableMemory.size() < additionalSegments) {
for (int i = 0; i < numPartitions; i++) {
compactPartition(i);
if(this.availableMemory.size() >= additionalSegments) {
break;
}
}
}
if (this.availableMemory.size() < additionalSegments || this.closed) {
return false;
}
else {
this.isResizing = true;
// allocate new buckets
final int startOffset = (this.numBuckets * HASH_BUCKET_SIZE) % this.segmentSize;
final int oldNumBuckets = this.numBuckets;
final int oldNumSegments = this.buckets.length;
MemorySegment[] mergedBuckets = new MemorySegment[newNumSegments];
System.arraycopy(this.buckets, 0, mergedBuckets, 0, this.buckets.length);
this.buckets = mergedBuckets;
this.numBuckets = newNumBuckets;
// initialize all new buckets
boolean oldSegment = (startOffset != 0);
final int startSegment = oldSegment ? (oldNumSegments-1) : oldNumSegments;
for (int i = startSegment, bucket = oldNumBuckets; i < newNumSegments && bucket < this.numBuckets; i++) {
MemorySegment seg;
int bucketOffset;
if(oldSegment) { // the first couple of new buckets may be located on an old segment
seg = this.buckets[i];
for (int k = (oldNumBuckets % bucketsPerSegment) ; k < bucketsPerSegment && bucket < this.numBuckets; k++, bucket++) {
bucketOffset = k * HASH_BUCKET_SIZE;
// initialize the header fields
seg.put(bucketOffset + HEADER_PARTITION_OFFSET, assignPartition(bucket, (byte)numPartitions));
seg.putInt(bucketOffset + HEADER_COUNT_OFFSET, 0);
seg.putLong(bucketOffset + HEADER_FORWARD_OFFSET, BUCKET_FORWARD_POINTER_NOT_SET);
}
} else {
seg = getNextBuffer();
// go over all buckets in the segment
for (int k = 0; k < bucketsPerSegment && bucket < this.numBuckets; k++, bucket++) {
bucketOffset = k * HASH_BUCKET_SIZE;
// initialize the header fields
seg.put(bucketOffset + HEADER_PARTITION_OFFSET, assignPartition(bucket, (byte)numPartitions));
seg.putInt(bucketOffset + HEADER_COUNT_OFFSET, 0);
seg.putLong(bucketOffset + HEADER_FORWARD_OFFSET, BUCKET_FORWARD_POINTER_NOT_SET);
}
}
this.buckets[i] = seg;
oldSegment = false; // we write on at most one old segment
}
int hashOffset;
int hash;
int pointerOffset;
long pointer;
IntArrayList hashList = new IntArrayList(NUM_ENTRIES_PER_BUCKET);
LongArrayList pointerList = new LongArrayList(NUM_ENTRIES_PER_BUCKET);
IntArrayList overflowHashes = new IntArrayList(64);
LongArrayList overflowPointers = new LongArrayList(64);
// go over all buckets and split them between old and new buckets
for (int i = 0; i < numPartitions; i++) {
InMemoryPartition<T> partition = this.partitions.get(i);
final MemorySegment[] overflowSegments = partition.overflowSegments;
int posHashCode;
for (int j = 0, bucket = i; j < this.buckets.length && bucket < oldNumBuckets; j++) {
MemorySegment segment = this.buckets[j];
// go over all buckets in the segment belonging to the partition
for (int k = bucket % bucketsPerSegment; k < bucketsPerSegment && bucket < oldNumBuckets; k += numPartitions, bucket += numPartitions) {
int bucketOffset = k * HASH_BUCKET_SIZE;
if((int)segment.get(bucketOffset + HEADER_PARTITION_OFFSET) != i) {
throw new IOException("Accessed wrong bucket! wanted: " + i + " got: " + segment.get(bucketOffset + HEADER_PARTITION_OFFSET));
}
// loop over all segments that are involved in the bucket (original bucket plus overflow buckets)
int countInSegment = segment.getInt(bucketOffset + HEADER_COUNT_OFFSET);
int numInSegment = 0;
pointerOffset = bucketOffset + BUCKET_POINTER_START_OFFSET;
hashOffset = bucketOffset + BUCKET_HEADER_LENGTH;
while (true) {
while (numInSegment < countInSegment) {
hash = segment.getInt(hashOffset);
if((hash % this.numBuckets) != bucket && (hash % this.numBuckets) != (bucket+oldNumBuckets)) {
throw new IOException("wanted: " + bucket + " or " + (bucket + oldNumBuckets) + " got: " + hash%this.numBuckets);
}
pointer = segment.getLong(pointerOffset);
hashList.add(hash);
pointerList.add(pointer);
pointerOffset += POINTER_LEN;
hashOffset += HASH_CODE_LEN;
numInSegment++;
}
// this segment is done. check if there is another chained bucket
final long forwardPointer = segment.getLong(bucketOffset + HEADER_FORWARD_OFFSET);
if (forwardPointer == BUCKET_FORWARD_POINTER_NOT_SET) {
break;
}
final int overflowSegNum = (int) (forwardPointer >>> 32);
segment = overflowSegments[overflowSegNum];
bucketOffset = (int) forwardPointer;
countInSegment = segment.getInt(bucketOffset + HEADER_COUNT_OFFSET);
pointerOffset = bucketOffset + BUCKET_POINTER_START_OFFSET;
hashOffset = bucketOffset + BUCKET_HEADER_LENGTH;
numInSegment = 0;
}
segment = this.buckets[j];
bucketOffset = k * HASH_BUCKET_SIZE;
// reset bucket for re-insertion
segment.putInt(bucketOffset + HEADER_COUNT_OFFSET, 0);
segment.putLong(bucketOffset + HEADER_FORWARD_OFFSET, BUCKET_FORWARD_POINTER_NOT_SET);
// refill table
if(hashList.size() != pointerList.size()) {
throw new IOException("Pointer and hash counts do not match. hashes: " + hashList.size() + " pointer: " + pointerList.size());
}
int newSegmentIndex = (bucket + oldNumBuckets) / bucketsPerSegment;
MemorySegment newSegment = this.buckets[newSegmentIndex];
// we need to avoid overflows in the first run
int oldBucketCount = 0;
int newBucketCount = 0;
while (!hashList.isEmpty()) {
hash = hashList.removeLast();
pointer = pointerList.removeLong(pointerList.size()-1);
posHashCode = hash % this.numBuckets;
if (posHashCode == bucket && oldBucketCount < NUM_ENTRIES_PER_BUCKET) {
bucketOffset = (bucket % bucketsPerSegment) * HASH_BUCKET_SIZE;
insertBucketEntryFromStart(segment, bucketOffset, hash, pointer, partition.getPartitionNumber());
oldBucketCount++;
}
else if (posHashCode == (bucket + oldNumBuckets) && newBucketCount < NUM_ENTRIES_PER_BUCKET) {
bucketOffset = ((bucket + oldNumBuckets) % bucketsPerSegment) * HASH_BUCKET_SIZE;
insertBucketEntryFromStart(newSegment, bucketOffset, hash, pointer, partition.getPartitionNumber());
newBucketCount++;
}
else if (posHashCode == (bucket + oldNumBuckets) || posHashCode == bucket) {
overflowHashes.add(hash);
overflowPointers.add(pointer);
}
else {
throw new IOException("Accessed wrong bucket. Target: " + bucket + " or " + (bucket + oldNumBuckets) + " Hit: " + posHashCode);
}
}
hashList.clear();
pointerList.clear();
}
}
// reset partition's overflow buckets and reclaim their memory
this.availableMemory.addAll(partition.resetOverflowBuckets());
// clear overflow lists
int bucketArrayPos;
int bucketInSegmentPos;
MemorySegment bucket;
while(!overflowHashes.isEmpty()) {
hash = overflowHashes.removeLast();
pointer = overflowPointers.removeLong(overflowPointers.size()-1);
posHashCode = hash % this.numBuckets;
bucketArrayPos = posHashCode >>> this.bucketsPerSegmentBits;
bucketInSegmentPos = (posHashCode & this.bucketsPerSegmentMask) << NUM_INTRA_BUCKET_BITS;
bucket = this.buckets[bucketArrayPos];
insertBucketEntryFromStart(bucket, bucketInSegmentPos, hash, pointer, partition.getPartitionNumber());
}
overflowHashes.clear();
overflowPointers.clear();
}
this.isResizing = false;
return true;
}
}
/**
* Compacts (garbage collects) partition with copy-compact strategy using compaction partition
*
* @param partitionNumber partition to compact
* @throws IOException
*/
private void compactPartition(final int partitionNumber) throws IOException {
// do nothing if table was closed, parameter is invalid or no garbage exists
if (this.closed || partitionNumber >= this.partitions.size() || this.partitions.get(partitionNumber).isCompacted()) {
return;
}
// release all segments owned by compaction partition
this.compactionMemory.clearAllMemory(availableMemory);
this.compactionMemory.allocateSegments(1);
this.compactionMemory.pushDownPages();
T tempHolder = this.buildSideSerializer.createInstance();
final int numPartitions = this.partitions.size();
InMemoryPartition<T> partition = this.partitions.remove(partitionNumber);
MemorySegment[] overflowSegments = partition.overflowSegments;
long pointer;
int pointerOffset;
int bucketOffset;
final int bucketsPerSegment = this.bucketsPerSegmentMask + 1;
for (int i = 0, bucket = partitionNumber; i < this.buckets.length && bucket < this.numBuckets; i++) {
MemorySegment segment = this.buckets[i];
// go over all buckets in the segment belonging to the partition
for (int k = bucket % bucketsPerSegment; k < bucketsPerSegment && bucket < this.numBuckets; k += numPartitions, bucket += numPartitions) {
bucketOffset = k * HASH_BUCKET_SIZE;
if((int)segment.get(bucketOffset + HEADER_PARTITION_OFFSET) != partitionNumber) {
throw new IOException("Accessed wrong bucket! wanted: " + partitionNumber + " got: " + segment.get(bucketOffset + HEADER_PARTITION_OFFSET));
}
// loop over all segments that are involved in the bucket (original bucket plus overflow buckets)
int countInSegment = segment.getInt(bucketOffset + HEADER_COUNT_OFFSET);
int numInSegment = 0;
pointerOffset = bucketOffset + BUCKET_POINTER_START_OFFSET;
while (true) {
while (numInSegment < countInSegment) {
pointer = segment.getLong(pointerOffset);
tempHolder = partition.readRecordAt(pointer, tempHolder);
pointer = this.compactionMemory.appendRecord(tempHolder);
segment.putLong(pointerOffset, pointer);
pointerOffset += POINTER_LEN;
numInSegment++;
}
// this segment is done. check if there is another chained bucket
final long forwardPointer = segment.getLong(bucketOffset + HEADER_FORWARD_OFFSET);
if (forwardPointer == BUCKET_FORWARD_POINTER_NOT_SET) {
break;
}
final int overflowSegNum = (int) (forwardPointer >>> 32);
segment = overflowSegments[overflowSegNum];
bucketOffset = (int) forwardPointer;
countInSegment = segment.getInt(bucketOffset + HEADER_COUNT_OFFSET);
pointerOffset = bucketOffset + BUCKET_POINTER_START_OFFSET;
numInSegment = 0;
}
segment = this.buckets[i];
}
}
// swap partition with compaction partition
this.compactionMemory.setPartitionNumber(partitionNumber);
this.partitions.add(partitionNumber, compactionMemory);
this.partitions.get(partitionNumber).overflowSegments = partition.overflowSegments;
this.partitions.get(partitionNumber).numOverflowSegments = partition.numOverflowSegments;
this.partitions.get(partitionNumber).nextOverflowBucket = partition.nextOverflowBucket;
this.partitions.get(partitionNumber).setIsCompacted(true);
//this.partitions.get(partitionNumber).pushDownPages();
this.compactionMemory = partition;
this.compactionMemory.resetRecordCounter();
this.compactionMemory.setPartitionNumber(-1);
this.compactionMemory.overflowSegments = null;
this.compactionMemory.numOverflowSegments = 0;
this.compactionMemory.nextOverflowBucket = 0;
// try to allocate maximum segment count
this.compactionMemory.clearAllMemory(this.availableMemory);
int maxSegmentNumber = this.getMaxPartition();
this.compactionMemory.allocateSegments(maxSegmentNumber);
this.compactionMemory.resetRWViews();
this.compactionMemory.pushDownPages();
}
/**
* Iterator that traverses the whole hash table once
*
* If entries are inserted during iteration they may be overlooked by the iterator
*/
public class EntryIterator implements MutableObjectIterator<T> {
private CompactingHashTable<T> table;
private ArrayList<T> cache; // holds full bucket including its overflow buckets
private int currentBucketIndex = 0;
private int currentSegmentIndex = 0;
private int currentBucketOffset = 0;
private int bucketsPerSegment;
private boolean done;
private EntryIterator(CompactingHashTable<T> compactingHashTable) {
this.table = compactingHashTable;
this.cache = new ArrayList<T>(64);
this.done = false;
this.bucketsPerSegment = table.bucketsPerSegmentMask + 1;
}
@Override
public T next(T reuse) throws IOException {
return next();
}
@Override
public T next() throws IOException {
if (done || this.table.closed) {
return null;
} else if(!cache.isEmpty()) {
return cache.remove(cache.size()-1);
} else {
while(!done && cache.isEmpty()) {
done = !fillCache();
}
if(!done) {
return cache.remove(cache.size()-1);
} else {
return null;
}
}
}
/**
* utility function that inserts all entries from a bucket and its overflow buckets into the cache
*
* @return true if last bucket was not reached yet
* @throws IOException
*/
private boolean fillCache() throws IOException {
if(currentBucketIndex >= table.numBuckets) {
return false;
}
MemorySegment bucket = table.buckets[currentSegmentIndex];
// get the basic characteristics of the bucket
final int partitionNumber = bucket.get(currentBucketOffset + HEADER_PARTITION_OFFSET);
final InMemoryPartition<T> partition = table.partitions.get(partitionNumber);
final MemorySegment[] overflowSegments = partition.overflowSegments;
int countInSegment = bucket.getInt(currentBucketOffset + HEADER_COUNT_OFFSET);
int numInSegment = 0;
int posInSegment = currentBucketOffset + BUCKET_POINTER_START_OFFSET;
int bucketOffset = currentBucketOffset;
// loop over all segments that are involved in the bucket (original bucket plus overflow buckets)
while (true) {
while (numInSegment < countInSegment) {
long pointer = bucket.getLong(posInSegment);
posInSegment += POINTER_LEN;
numInSegment++;
T target = table.buildSideSerializer.createInstance();
try {
target = partition.readRecordAt(pointer, target);
cache.add(target);
} catch (IOException e) {
throw new RuntimeException("Error deserializing record from the Hash Table: " + e.getMessage(), e);
}
}
// this segment is done. check if there is another chained bucket
final long forwardPointer = bucket.getLong(bucketOffset + HEADER_FORWARD_OFFSET);
if (forwardPointer == BUCKET_FORWARD_POINTER_NOT_SET) {
break;
}
final int overflowSegNum = (int) (forwardPointer >>> 32);
bucket = overflowSegments[overflowSegNum];
bucketOffset = (int) forwardPointer;
countInSegment = bucket.getInt(bucketOffset + HEADER_COUNT_OFFSET);
posInSegment = bucketOffset + BUCKET_POINTER_START_OFFSET;
numInSegment = 0;
}
currentBucketIndex++;
if(currentBucketIndex % bucketsPerSegment == 0) {
currentSegmentIndex++;
currentBucketOffset = 0;
} else {
currentBucketOffset += HASH_BUCKET_SIZE;
}
return true;
}
}
public final class HashTableProber<PT> extends AbstractHashTableProber<PT, T>{
private InMemoryPartition<T> partition;
private MemorySegment bucket;
private int pointerOffsetInBucket;
private HashTableProber(TypeComparator<PT> probeTypeComparator, TypePairComparator<PT, T> pairComparator)
{
super(probeTypeComparator, pairComparator);
}
public T getMatchFor(PT probeSideRecord, T reuse) {
if (closed) {
return null;
}
final int searchHashCode = MathUtils.jenkinsHash(this.probeTypeComparator.hash(probeSideRecord));
final int posHashCode = searchHashCode % numBuckets;
// get the bucket for the given hash code
MemorySegment bucket = buckets[posHashCode >> bucketsPerSegmentBits];
int bucketInSegmentOffset = (posHashCode & bucketsPerSegmentMask) << NUM_INTRA_BUCKET_BITS;
// get the basic characteristics of the bucket
final int partitionNumber = bucket.get(bucketInSegmentOffset + HEADER_PARTITION_OFFSET);
final InMemoryPartition<T> p = partitions.get(partitionNumber);
final MemorySegment[] overflowSegments = p.overflowSegments;
this.pairComparator.setReference(probeSideRecord);
int countInSegment = bucket.getInt(bucketInSegmentOffset + HEADER_COUNT_OFFSET);
int numInSegment = 0;
int posInSegment = bucketInSegmentOffset + BUCKET_HEADER_LENGTH;
// loop over all segments that are involved in the bucket (original bucket plus overflow buckets)
while (true) {
while (numInSegment < countInSegment) {
final int thisCode = bucket.getInt(posInSegment);
posInSegment += HASH_CODE_LEN;
// check if the hash code matches
if (thisCode == searchHashCode) {
// get the pointer to the pair
final int pointerOffset = bucketInSegmentOffset + BUCKET_POINTER_START_OFFSET + (numInSegment * POINTER_LEN);
final long pointer = bucket.getLong(pointerOffset);
numInSegment++;
// deserialize the key to check whether it is really equal, or whether we had only a hash collision
try {
reuse = p.readRecordAt(pointer, reuse);
if (this.pairComparator.equalToReference(reuse)) {
this.partition = p;
this.bucket = bucket;
this.pointerOffsetInBucket = pointerOffset;
return reuse;
}
}
catch (IOException e) {
throw new RuntimeException("Error deserializing record from the hashtable: " + e.getMessage(), e);
}
}
else {
numInSegment++;
}
}
// this segment is done. check if there is another chained bucket
final long forwardPointer = bucket.getLong(bucketInSegmentOffset + HEADER_FORWARD_OFFSET);
if (forwardPointer == BUCKET_FORWARD_POINTER_NOT_SET) {
return null;
}
final int overflowSegNum = (int) (forwardPointer >>> 32);
bucket = overflowSegments[overflowSegNum];
bucketInSegmentOffset = (int) forwardPointer;
countInSegment = bucket.getInt(bucketInSegmentOffset + HEADER_COUNT_OFFSET);
posInSegment = bucketInSegmentOffset + BUCKET_HEADER_LENGTH;
numInSegment = 0;
}
}
public T getMatchFor(PT probeSideRecord) {
if (closed) {
return null;
}
final int searchHashCode = MathUtils.jenkinsHash(this.probeTypeComparator.hash(probeSideRecord));
final int posHashCode = searchHashCode % numBuckets;
// get the bucket for the given hash code
MemorySegment bucket = buckets[posHashCode >> bucketsPerSegmentBits];
int bucketInSegmentOffset = (posHashCode & bucketsPerSegmentMask) << NUM_INTRA_BUCKET_BITS;
// get the basic characteristics of the bucket
final int partitionNumber = bucket.get(bucketInSegmentOffset + HEADER_PARTITION_OFFSET);
final InMemoryPartition<T> p = partitions.get(partitionNumber);
final MemorySegment[] overflowSegments = p.overflowSegments;
this.pairComparator.setReference(probeSideRecord);
int countInSegment = bucket.getInt(bucketInSegmentOffset + HEADER_COUNT_OFFSET);
int numInSegment = 0;
int posInSegment = bucketInSegmentOffset + BUCKET_HEADER_LENGTH;
// loop over all segments that are involved in the bucket (original bucket plus overflow buckets)
while (true) {
while (numInSegment < countInSegment) {
final int thisCode = bucket.getInt(posInSegment);
posInSegment += HASH_CODE_LEN;
// check if the hash code matches
if (thisCode == searchHashCode) {
// get the pointer to the pair
final int pointerOffset = bucketInSegmentOffset + BUCKET_POINTER_START_OFFSET + (numInSegment * POINTER_LEN);
final long pointer = bucket.getLong(pointerOffset);
numInSegment++;
// deserialize the key to check whether it is really equal, or whether we had only a hash collision
try {
T result = p.readRecordAt(pointer);
if (this.pairComparator.equalToReference(result)) {
this.partition = p;
this.bucket = bucket;
this.pointerOffsetInBucket = pointerOffset;
return result;
}
}
catch (IOException e) {
throw new RuntimeException("Error deserializing record from the hashtable: " + e.getMessage(), e);
}
}
else {
numInSegment++;
}
}
// this segment is done. check if there is another chained bucket
final long forwardPointer = bucket.getLong(bucketInSegmentOffset + HEADER_FORWARD_OFFSET);
if (forwardPointer == BUCKET_FORWARD_POINTER_NOT_SET) {
return null;
}
final int overflowSegNum = (int) (forwardPointer >>> 32);
bucket = overflowSegments[overflowSegNum];
bucketInSegmentOffset = (int) forwardPointer;
countInSegment = bucket.getInt(bucketInSegmentOffset + HEADER_COUNT_OFFSET);
posInSegment = bucketInSegmentOffset + BUCKET_HEADER_LENGTH;
numInSegment = 0;
}
}
public void updateMatch(T record) throws IOException {
if (closed) {
return;
}
long newPointer = insertRecordIntoPartition(record, this.partition, true);
this.bucket.putLong(this.pointerOffsetInBucket, newPointer);
}
}
}