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/*
* 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.spark.util.collection.unsafe.sort;
import java.util.Comparator;
import org.apache.avro.reflect.Nullable;
import org.apache.spark.memory.MemoryConsumer;
import org.apache.spark.memory.TaskMemoryManager;
import org.apache.spark.unsafe.Platform;
import org.apache.spark.unsafe.array.LongArray;
import org.apache.spark.util.collection.Sorter;
/**
* Sorts records using an AlphaSort-style key-prefix sort. This sort stores pointers to records
* alongside a user-defined prefix of the record's sorting key. When the underlying sort algorithm
* compares records, it will first compare the stored key prefixes; if the prefixes are not equal,
* then we do not need to traverse the record pointers to compare the actual records. Avoiding these
* random memory accesses improves cache hit rates.
*/
public final class UnsafeInMemorySorter {
private static final class SortComparator implements Comparator<RecordPointerAndKeyPrefix> {
private final RecordComparator recordComparator;
private final PrefixComparator prefixComparator;
private final TaskMemoryManager memoryManager;
SortComparator(
RecordComparator recordComparator,
PrefixComparator prefixComparator,
TaskMemoryManager memoryManager) {
this.recordComparator = recordComparator;
this.prefixComparator = prefixComparator;
this.memoryManager = memoryManager;
}
@Override
public int compare(RecordPointerAndKeyPrefix r1, RecordPointerAndKeyPrefix r2) {
final int prefixComparisonResult = prefixComparator.compare(r1.keyPrefix, r2.keyPrefix);
if (prefixComparisonResult == 0) {
final Object baseObject1 = memoryManager.getPage(r1.recordPointer);
final long baseOffset1 = memoryManager.getOffsetInPage(r1.recordPointer) + 4; // skip length
final Object baseObject2 = memoryManager.getPage(r2.recordPointer);
final long baseOffset2 = memoryManager.getOffsetInPage(r2.recordPointer) + 4; // skip length
return recordComparator.compare(baseObject1, baseOffset1, baseObject2, baseOffset2);
} else {
return prefixComparisonResult;
}
}
}
private final MemoryConsumer consumer;
private final TaskMemoryManager memoryManager;
@Nullable
private final Sorter<RecordPointerAndKeyPrefix, LongArray> sorter;
@Nullable
private final Comparator<RecordPointerAndKeyPrefix> sortComparator;
/**
* Within this buffer, position {@code 2 * i} holds a pointer pointer to the record at
* index {@code i}, while position {@code 2 * i + 1} in the array holds an 8-byte key prefix.
*/
private LongArray array;
/**
* The position in the sort buffer where new records can be inserted.
*/
private int pos = 0;
public UnsafeInMemorySorter(
final MemoryConsumer consumer,
final TaskMemoryManager memoryManager,
final RecordComparator recordComparator,
final PrefixComparator prefixComparator,
int initialSize) {
this(consumer, memoryManager, recordComparator, prefixComparator,
consumer.allocateArray(initialSize * 2));
}
public UnsafeInMemorySorter(
final MemoryConsumer consumer,
final TaskMemoryManager memoryManager,
final RecordComparator recordComparator,
final PrefixComparator prefixComparator,
LongArray array) {
this.consumer = consumer;
this.memoryManager = memoryManager;
if (recordComparator != null) {
this.sorter = new Sorter<>(UnsafeSortDataFormat.INSTANCE);
this.sortComparator = new SortComparator(recordComparator, prefixComparator, memoryManager);
} else {
this.sorter = null;
this.sortComparator = null;
}
this.array = array;
}
/**
* Free the memory used by pointer array.
*/
public void free() {
if (consumer != null) {
consumer.freeArray(array);
array = null;
}
}
public void reset() {
pos = 0;
}
/**
* @return the number of records that have been inserted into this sorter.
*/
public int numRecords() {
return pos / 2;
}
public long getMemoryUsage() {
return array.size() * 8L;
}
public boolean hasSpaceForAnotherRecord() {
return pos + 2 <= array.size();
}
public void expandPointerArray(LongArray newArray) {
if (newArray.size() < array.size()) {
throw new OutOfMemoryError("Not enough memory to grow pointer array");
}
Platform.copyMemory(
array.getBaseObject(),
array.getBaseOffset(),
newArray.getBaseObject(),
newArray.getBaseOffset(),
array.size() * 8L);
consumer.freeArray(array);
array = newArray;
}
/**
* Inserts a record to be sorted. Assumes that the record pointer points to a record length
* stored as a 4-byte integer, followed by the record's bytes.
*
* @param recordPointer pointer to a record in a data page, encoded by {@link TaskMemoryManager}.
* @param keyPrefix a user-defined key prefix
*/
public void insertRecord(long recordPointer, long keyPrefix) {
if (!hasSpaceForAnotherRecord()) {
expandPointerArray(consumer.allocateArray(array.size() * 2));
}
array.set(pos, recordPointer);
pos++;
array.set(pos, keyPrefix);
pos++;
}
public final class SortedIterator extends UnsafeSorterIterator {
private final int numRecords;
private int position;
private Object baseObject;
private long baseOffset;
private long keyPrefix;
private int recordLength;
private SortedIterator(int numRecords) {
this.numRecords = numRecords;
this.position = 0;
}
public SortedIterator clone() {
SortedIterator iter = new SortedIterator(numRecords);
iter.position = position;
iter.baseObject = baseObject;
iter.baseOffset = baseOffset;
iter.keyPrefix = keyPrefix;
iter.recordLength = recordLength;
return iter;
}
@Override
public int getNumRecords() {
return numRecords;
}
@Override
public boolean hasNext() {
return position / 2 < numRecords;
}
@Override
public void loadNext() {
// This pointer points to a 4-byte record length, followed by the record's bytes
final long recordPointer = array.get(position);
baseObject = memoryManager.getPage(recordPointer);
baseOffset = memoryManager.getOffsetInPage(recordPointer) + 4; // Skip over record length
recordLength = Platform.getInt(baseObject, baseOffset - 4);
keyPrefix = array.get(position + 1);
position += 2;
}
@Override
public Object getBaseObject() { return baseObject; }
@Override
public long getBaseOffset() { return baseOffset; }
@Override
public int getRecordLength() { return recordLength; }
@Override
public long getKeyPrefix() { return keyPrefix; }
}
/**
* Return an iterator over record pointers in sorted order. For efficiency, all calls to
* {@code next()} will return the same mutable object.
*/
public SortedIterator getSortedIterator() {
if (sorter != null) {
sorter.sort(array, 0, pos / 2, sortComparator);
}
return new SortedIterator(pos / 2);
}
}
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