spark UnsafeInMemorySorter 源码

spark UnsafeInMemorySorter 代码

文件路径：/core/src/main/java/org/apache/spark/util/collection/unsafe/sort/UnsafeInMemorySorter.java

/*
 * 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 java.util.LinkedList;

import javax.annotation.Nullable;

import org.apache.spark.TaskContext;
import org.apache.spark.memory.MemoryConsumer;
import org.apache.spark.memory.SparkOutOfMemoryError;
import org.apache.spark.memory.TaskMemoryManager;
import org.apache.spark.unsafe.Platform;
import org.apache.spark.unsafe.UnsafeAlignedOffset;
import org.apache.spark.unsafe.array.LongArray;
import org.apache.spark.unsafe.memory.MemoryBlock;
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);
      int uaoSize = UnsafeAlignedOffset.getUaoSize();
      if (prefixComparisonResult == 0) {
        final Object baseObject1 = memoryManager.getPage(r1.recordPointer);
        final long baseOffset1 = memoryManager.getOffsetInPage(r1.recordPointer) + uaoSize;
        final int baseLength1 = UnsafeAlignedOffset.getSize(baseObject1, baseOffset1 - uaoSize);
        final Object baseObject2 = memoryManager.getPage(r2.recordPointer);
        final long baseOffset2 = memoryManager.getOffsetInPage(r2.recordPointer) + uaoSize;
        final int baseLength2 = UnsafeAlignedOffset.getSize(baseObject2, baseOffset2 - uaoSize);
        return recordComparator.compare(baseObject1, baseOffset1, baseLength1, baseObject2,
          baseOffset2, baseLength2);
      } else {
        return prefixComparisonResult;
      }
    }
  }

  private final MemoryConsumer consumer;
  private final TaskMemoryManager memoryManager;
  @Nullable
  private final Comparator<RecordPointerAndKeyPrefix> sortComparator;

  /**
   * If non-null, specifies the radix sort parameters and that radix sort will be used.
   */
  @Nullable
  private final PrefixComparators.RadixSortSupport radixSortSupport;

  /**
   * Within this buffer, position {@code 2 * i} holds a pointer to the record at
   * index {@code i}, while position {@code 2 * i + 1} in the array holds an 8-byte key prefix.
   *
   * Only part of the array will be used to store the pointers, the rest part is preserved as
   * temporary buffer for sorting.
   */
  private LongArray array;

  /**
   * The position in the sort buffer where new records can be inserted.
   */
  private int pos = 0;

  /**
   * If sorting with radix sort, specifies the starting position in the sort buffer where records
   * with non-null prefixes are kept. Positions [0..nullBoundaryPos) will contain null-prefixed
   * records, and positions [nullBoundaryPos..pos) non-null prefixed records. This lets us avoid
   * radix sorting over null values.
   */
  private int nullBoundaryPos = 0;

  /*
   * How many records could be inserted, because part of the array should be left for sorting.
   */
  private int usableCapacity = 0;

  private long initialSize;

  private long totalSortTimeNanos = 0L;

  public UnsafeInMemorySorter(
    final MemoryConsumer consumer,
    final TaskMemoryManager memoryManager,
    final RecordComparator recordComparator,
    final PrefixComparator prefixComparator,
    int initialSize,
    boolean canUseRadixSort) {
    this(consumer, memoryManager, recordComparator, prefixComparator,
      consumer.allocateArray(initialSize * 2L), canUseRadixSort);
  }

  public UnsafeInMemorySorter(
      final MemoryConsumer consumer,
      final TaskMemoryManager memoryManager,
      final RecordComparator recordComparator,
      final PrefixComparator prefixComparator,
      LongArray array,
      boolean canUseRadixSort) {
    this.consumer = consumer;
    this.memoryManager = memoryManager;
    this.initialSize = array.size();
    if (recordComparator != null) {
      this.sortComparator = new SortComparator(recordComparator, prefixComparator, memoryManager);
      if (canUseRadixSort && prefixComparator instanceof PrefixComparators.RadixSortSupport) {
        this.radixSortSupport = (PrefixComparators.RadixSortSupport)prefixComparator;
      } else {
        this.radixSortSupport = null;
      }
    } else {
      this.sortComparator = null;
      this.radixSortSupport = null;
    }
    this.array = array;
    this.usableCapacity = getUsableCapacity();
  }

  private int getUsableCapacity() {
    // Radix sort requires same amount of used memory as buffer, Tim sort requires
    // half of the used memory as buffer.
    return (int) (array.size() / (radixSortSupport != null ? 2 : 1.5));
  }

  public long getInitialSize() {
    return initialSize;
  }

  /**
   * Free the memory used by pointer array.
   */
  public void freeMemory() {
    if (consumer != null) {
      if (array != null) {
        consumer.freeArray(array);
      }

      // Set the array to null instead of allocating a new array. Allocating an array could have
      // triggered another spill and this method already is called from UnsafeExternalSorter when
      // spilling. Attempting to allocate while spilling is dangerous, as we could be holding onto
      // a large partially complete allocation, which may prevent other memory from being allocated.
      // Instead we will allocate the new array when it is necessary.
      array = null;
      usableCapacity = 0;
    }
    pos = 0;
    nullBoundaryPos = 0;
  }

  /**
   * @return the number of records that have been inserted into this sorter.
   */
  public int numRecords() {
    return pos / 2;
  }

  /**
   * @return the total amount of time spent sorting data (in-memory only).
   */
  public long getSortTimeNanos() {
    return totalSortTimeNanos;
  }

  public long getMemoryUsage() {
    if (array == null) {
      return 0L;
    }

    return array.size() * 8;
  }

  public boolean hasSpaceForAnotherRecord() {
    return pos + 1 < usableCapacity;
  }

  public void expandPointerArray(LongArray newArray) {
    if (array != null) {
      if (newArray.size() < array.size()) {
        // checkstyle.off: RegexpSinglelineJava
        throw new SparkOutOfMemoryError("Not enough memory to grow pointer array");
        // checkstyle.on: RegexpSinglelineJava
      }
      Platform.copyMemory(
        array.getBaseObject(),
        array.getBaseOffset(),
        newArray.getBaseObject(),
        newArray.getBaseOffset(),
        pos * 8L);
      consumer.freeArray(array);
    }
    array = newArray;
    usableCapacity = getUsableCapacity();
  }

  /**
   * Inserts a record to be sorted. Assumes that the record pointer points to a record length
   * stored as a uaoSize(4 or 8) bytes 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, boolean prefixIsNull) {
    if (!hasSpaceForAnotherRecord()) {
      throw new IllegalStateException("There is no space for new record");
    }
    if (prefixIsNull && radixSortSupport != null) {
      // Swap forward a non-null record to make room for this one at the beginning of the array.
      array.set(pos, array.get(nullBoundaryPos));
      pos++;
      array.set(pos, array.get(nullBoundaryPos + 1));
      pos++;
      // Place this record in the vacated position.
      array.set(nullBoundaryPos, recordPointer);
      nullBoundaryPos++;
      array.set(nullBoundaryPos, keyPrefix);
      nullBoundaryPos++;
    } else {
      array.set(pos, recordPointer);
      pos++;
      array.set(pos, keyPrefix);
      pos++;
    }
  }

  public final class SortedIterator extends UnsafeSorterIterator implements Cloneable {

    private final int numRecords;
    private int position;
    private int offset;
    private Object baseObject;
    private long baseOffset;
    private long keyPrefix;
    private int recordLength;
    private long currentPageNumber;
    private final TaskContext taskContext = TaskContext.get();

    private SortedIterator(int numRecords, int offset) {
      this.numRecords = numRecords;
      this.position = 0;
      this.offset = offset;
    }

    @Override
    public SortedIterator clone() {
      SortedIterator iter = new SortedIterator(numRecords, offset);
      iter.position = position;
      iter.baseObject = baseObject;
      iter.baseOffset = baseOffset;
      iter.keyPrefix = keyPrefix;
      iter.recordLength = recordLength;
      iter.currentPageNumber = currentPageNumber;
      return iter;
    }

    @Override
    public int getNumRecords() {
      return numRecords;
    }

    @Override
    public boolean hasNext() {
      return position / 2 < numRecords;
    }

    @Override
    public void loadNext() {
      // Kill the task in case it has been marked as killed. This logic is from
      // InterruptibleIterator, but we inline it here instead of wrapping the iterator in order
      // to avoid performance overhead. This check is added here in `loadNext()` instead of in
      // `hasNext()` because it's technically possible for the caller to be relying on
      // `getNumRecords()` instead of `hasNext()` to know when to stop.
      if (taskContext != null) {
        taskContext.killTaskIfInterrupted();
      }
      // This pointer points to a 4-byte record length, followed by the record's bytes
      final long recordPointer = array.get(offset + position);
      currentPageNumber = TaskMemoryManager.decodePageNumber(recordPointer);
      int uaoSize = UnsafeAlignedOffset.getUaoSize();
      baseObject = memoryManager.getPage(recordPointer);
      // Skip over record length
      baseOffset = memoryManager.getOffsetInPage(recordPointer) + uaoSize;
      recordLength = UnsafeAlignedOffset.getSize(baseObject, baseOffset - uaoSize);
      keyPrefix = array.get(offset + position + 1);
      position += 2;
    }

    @Override
    public Object getBaseObject() { return baseObject; }

    @Override
    public long getBaseOffset() { return baseOffset; }

    @Override
    public long getCurrentPageNumber() {
      return currentPageNumber;
    }

    @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 UnsafeSorterIterator getSortedIterator() {
    if (numRecords() == 0) {
      // `array` might be null, so make sure that it is not accessed by returning early.
      return new SortedIterator(0, 0);
    }

    int offset = 0;
    long start = System.nanoTime();
    if (sortComparator != null) {
      if (this.radixSortSupport != null) {
        offset = RadixSort.sortKeyPrefixArray(
          array, nullBoundaryPos, (pos - nullBoundaryPos) / 2L, 0, 7,
          radixSortSupport.sortDescending(), radixSortSupport.sortSigned());
      } else {
        MemoryBlock unused = new MemoryBlock(
          array.getBaseObject(),
          array.getBaseOffset() + pos * 8L,
          (array.size() - pos) * 8L);
        LongArray buffer = new LongArray(unused);
        Sorter<RecordPointerAndKeyPrefix, LongArray> sorter =
          new Sorter<>(new UnsafeSortDataFormat(buffer));
        sorter.sort(array, 0, pos / 2, sortComparator);
      }
    }
    totalSortTimeNanos += System.nanoTime() - start;
    if (nullBoundaryPos > 0) {
      assert radixSortSupport != null : "Nulls are only stored separately with radix sort";
      LinkedList<UnsafeSorterIterator> queue = new LinkedList<>();

      // The null order is either LAST or FIRST, regardless of sorting direction (ASC|DESC)
      if (radixSortSupport.nullsFirst()) {
        queue.add(new SortedIterator(nullBoundaryPos / 2, 0));
        queue.add(new SortedIterator((pos - nullBoundaryPos) / 2, offset));
      } else {
        queue.add(new SortedIterator((pos - nullBoundaryPos) / 2, offset));
        queue.add(new SortedIterator(nullBoundaryPos / 2, 0));
      }
      return new UnsafeExternalSorter.ChainedIterator(queue);
    } else {
      return new SortedIterator(pos / 2, offset);
    }
  }
}

相关信息

spark 源码目录

相关文章

spark PrefixComparator 源码

spark PrefixComparators 源码

spark RadixSort 源码

spark RecordComparator 源码

spark RecordPointerAndKeyPrefix 源码

spark UnsafeExternalSorter 源码

spark UnsafeSortDataFormat 源码

spark UnsafeSorterIterator 源码

spark UnsafeSorterSpillMerger 源码

spark UnsafeSorterSpillReader 源码