eu.stratosphere.pact.runtime.hash.InMemoryPartition Maven / Gradle / Ivy
/***********************************************************************************************************************
* Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
*
* Licensed 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 eu.stratosphere.pact.runtime.hash;
import java.io.EOFException;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import eu.stratosphere.api.common.typeutils.TypeSerializer;
import eu.stratosphere.core.memory.MemorySegment;
import eu.stratosphere.core.memory.MemorySegmentSource;
import eu.stratosphere.core.memory.SeekableDataInputView;
import eu.stratosphere.nephele.services.memorymanager.AbstractPagedInputView;
import eu.stratosphere.nephele.services.memorymanager.AbstractPagedOutputView;
import eu.stratosphere.nephele.services.memorymanager.ListMemorySegmentSource;
/**
* In-memory partition with overflow buckets for {@link CompactingHashTable}
*
* @param T record type
*/
public class InMemoryPartition {
// --------------------------------- Table Structure Auxiliaries ------------------------------------
protected MemorySegment[] overflowSegments; // segments in which overflow buckets from the table structure are stored
protected int numOverflowSegments; // the number of actual segments in the overflowSegments array
protected int nextOverflowBucket; // the next free bucket in the current overflow segment
// ------------------------------------- Type Accessors --------------------------------------------
private final TypeSerializer serializer;
// -------------------------------------- Record Buffers --------------------------------------------
private final ArrayList partitionPages;
private final ListMemorySegmentSource availableMemory;
private final WriteView writeView;
private final ReadView readView;
private long recordCounter; // number of records in this partition including garbage
// ----------------------------------------- General ------------------------------------------------
private int partitionNumber; // the number of the partition
private boolean compacted; // overwritten records since allocation or last full compaction
// --------------------------------------------------------------------------------------------------
/**
* Creates a new partition, in memory, with one buffer.
*
* @param serializer Serializer for T.
* @param partitionNumber The number of the partition.
* @param memSource memory pool
* @param pageSize segment size in bytes
* @param pageSizeInBits
*/
public InMemoryPartition(TypeSerializer serializer, int partitionNumber,
ListMemorySegmentSource memSource, int pageSize, int pageSizeInBits)
{
this.overflowSegments = new MemorySegment[2];
this.numOverflowSegments = 0;
this.nextOverflowBucket = 0;
this.serializer = serializer;
this.partitionPages = new ArrayList(64);
this.availableMemory = memSource;
this.partitionNumber = partitionNumber;
// add the first segment
this.partitionPages.add(memSource.nextSegment());
// empty partitions have no garbage
this.compacted = true;
this.writeView = new WriteView(this.partitionPages, memSource, pageSize, pageSizeInBits);
this.readView = new ReadView(this.partitionPages, pageSize, pageSizeInBits);
}
// --------------------------------------------------------------------------------------------------
/**
* Gets the partition number of this partition.
*
* @return This partition's number.
*/
public int getPartitionNumber() {
return this.partitionNumber;
}
/**
* overwrites partition number and should only be used on compaction partition
* @param number new partition
*/
public void setPartitionNumber(int number) {
this.partitionNumber = number;
}
/**
*
* @return number of segments owned by partition
*/
public int getBlockCount() {
return this.partitionPages.size();
}
/**
* number of records in partition including garbage
*
* @return number record count
*/
public long getRecordCount() {
return this.recordCounter;
}
/**
* sets record counter to zero and should only be used on compaction partition
*/
public void resetRecordCounter() {
this.recordCounter = 0L;
}
/**
* @return true if garbage exists in partition
*/
public boolean isCompacted() {
return this.compacted;
}
/**
* sets compaction status (should only be set true directly after compaction and false when garbage was created)
*
* @param compacted compaction status
*/
public void setCompaction(boolean compacted) {
this.compacted = compacted;
}
// --------------------------------------------------------------------------------------------------
/**
* Inserts the given object into the current buffer. This method returns a pointer that
* can be used to address the written record in this partition.
*
* @param record The object to be written to the partition.
* @return A pointer to the object in the partition.
* @throws IOException Thrown when the write failed.
*/
public final long appendRecord(T record) throws IOException {
long pointer = this.writeView.getCurrentPointer();
try {
this.serializer.serialize(record, this.writeView);
this.recordCounter++;
return pointer;
}
catch (EOFException e) {
// we ran out of pages.
// first, reset the pages and then we need to trigger a compaction
//int oldCurrentBuffer =
this.writeView.resetTo(pointer);
//for (int bufNum = this.partitionPages.size() - 1; bufNum > oldCurrentBuffer; bufNum--) {
// this.availableMemory.addMemorySegment(this.partitionPages.remove(bufNum));
//}
throw e;
}
}
public void readRecordAt(long pointer, T record) throws IOException {
this.readView.setReadPosition(pointer);
this.serializer.deserialize(record, this.readView);
}
/**
* UNSAFE!! overwrites record
* causes inconsistency or data loss for overwriting everything but records of the exact same size
*
* @param pointer pointer to start of record
* @param record record to overwrite old one with
* @throws IOException
*/
@Deprecated
public void overwriteRecordAt(long pointer, T record) throws IOException {
long tmpPointer = this.writeView.getCurrentPointer();
this.writeView.resetTo(pointer);
this.serializer.serialize(record, this.writeView);
this.writeView.resetTo(tmpPointer);
}
/**
* releases all of the partition's segments (pages and overflow buckets)
*
* @param target memory pool to release segments to
*/
public void clearAllMemory(List target) {
// return the overflow segments
if (this.overflowSegments != null) {
for (int k = 0; k < this.numOverflowSegments; k++) {
target.add(this.overflowSegments[k]);
}
}
// return the partition buffers
target.addAll(this.partitionPages);
this.partitionPages.clear();
}
/**
* attempts to allocate specified number of segments and should only be used by compaction partition
* fails silently if not enough segments are available since next compaction could still succeed
*
* @param numberOfSegments allocation count
*/
public void allocateSegments(int numberOfSegments) {
while(getBlockCount() < numberOfSegments) {
MemorySegment next = this.availableMemory.nextSegment();
if(next != null) {
this.partitionPages.add(next);
} else {
return;
}
}
}
public void releaseSegments(int maxSegmentNumber, ArrayList target) {
while(getBlockCount() > maxSegmentNumber) {
target.add(partitionPages.remove(partitionPages.size()-1));
}
}
@Override
public String toString() {
return String.format("Partition %d - %d records, %d partition blocks, %d bucket overflow blocks", getPartitionNumber(), getRecordCount(), getBlockCount(), this.numOverflowSegments);
}
// ============================================================================================
private static final class WriteView extends AbstractPagedOutputView {
private final ArrayList pages;
private final MemorySegmentSource memSource;
private final int sizeBits;
private final int sizeMask;
private int currentPageNumber;
private int segmentNumberOffset;
private WriteView(ArrayList pages, MemorySegmentSource memSource,
int pageSize, int pageSizeBits)
{
super(pages.get(0), pageSize, 0);
this.pages = pages;
this.memSource = memSource;
this.sizeBits = pageSizeBits;
this.sizeMask = pageSize - 1;
}
@Override
protected MemorySegment nextSegment(MemorySegment current, int bytesUsed) throws IOException {
MemorySegment next = this.memSource.nextSegment();
if(next == null) {
throw new EOFException();
}
this.pages.add(next);
this.currentPageNumber++;
return next;
}
private long getCurrentPointer() {
return (((long) this.currentPageNumber) << this.sizeBits) + getCurrentPositionInSegment();
}
private int resetTo(long pointer) {
final int pageNum = (int) (pointer >>> this.sizeBits);
final int offset = (int) (pointer & this.sizeMask);
this.currentPageNumber = pageNum;
int posInArray = pageNum - this.segmentNumberOffset;
seekOutput(this.pages.get(posInArray), offset);
return posInArray;
}
public void setSegmentNumberOffset(int offset) {
this.segmentNumberOffset = offset;
}
}
private static final class ReadView extends AbstractPagedInputView implements SeekableDataInputView {
private final ArrayList segments;
private final int segmentSizeBits;
private final int segmentSizeMask;
private int currentSegmentIndex;
private int segmentNumberOffset;
public ReadView(ArrayList segments, int segmentSize, int segmentSizeBits) {
super(segments.get(0), segmentSize, 0);
if ((segmentSize & (segmentSize - 1)) != 0) {
throw new IllegalArgumentException("Segment size must be a power of 2!");
}
this.segments = segments;
this.segmentSizeBits = segmentSizeBits;
this.segmentSizeMask = segmentSize - 1;
}
@Override
protected MemorySegment nextSegment(MemorySegment current) throws EOFException {
if (++this.currentSegmentIndex < this.segments.size()) {
return this.segments.get(this.currentSegmentIndex);
} else {
throw new EOFException();
}
}
@Override
protected int getLimitForSegment(MemorySegment segment) {
return this.segmentSizeMask + 1;
}
@Override
public void setReadPosition(long position) {
final int bufferNum = ((int) (position >>> this.segmentSizeBits)) - this.segmentNumberOffset;
final int offset = (int) (position & this.segmentSizeMask);
this.currentSegmentIndex = bufferNum;
seekInput(this.segments.get(bufferNum), offset, this.segmentSizeMask + 1);
}
public void setSegmentNumberOffset(int offset) {
this.segmentNumberOffset = offset;
}
}
}
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