org.apache.flink.runtime.state.heap.HeapPriorityQueueSet Maven / Gradle / Ivy
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* 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,
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*/
package org.apache.flink.runtime.state.heap;
import org.apache.flink.runtime.state.KeyExtractorFunction;
import org.apache.flink.runtime.state.KeyGroupRange;
import org.apache.flink.runtime.state.KeyGroupRangeAssignment;
import org.apache.flink.runtime.state.KeyGroupedInternalPriorityQueue;
import org.apache.flink.runtime.state.PriorityComparator;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.HashMap;
import java.util.Set;
import static org.apache.flink.util.Preconditions.checkArgument;
/**
* A heap-based priority queue with set semantics, based on {@link HeapPriorityQueue}. The heap is supported by hash
* set for fast contains (de-duplication) and deletes. Object identification happens based on {@link #equals(Object)}.
*
* Possible future improvements:
*
* - We could also implement shrinking for the heap and the deduplication set.
* - We could replace the deduplication maps with more efficient custom implementations. In particular, a hash set
* would be enough if it could return existing elements on unsuccessful adding, etc..
*
*
* @param type of the contained elements.
*/
public class HeapPriorityQueueSet
extends HeapPriorityQueue
implements KeyGroupedInternalPriorityQueue {
/**
* Function to extract the key from contained elements.
*/
private final KeyExtractorFunction keyExtractor;
/**
* This array contains one hash set per key-group. The sets are used for fast de-duplication and deletes of elements.
*/
private final HashMap[] deduplicationMapsByKeyGroup;
/**
* The key-group range of elements that are managed by this queue.
*/
private final KeyGroupRange keyGroupRange;
/**
* The total number of key-groups of the job.
*/
private final int totalNumberOfKeyGroups;
/**
* Creates an empty {@link HeapPriorityQueueSet} with the requested initial capacity.
*
* @param elementPriorityComparator comparator for the priority of contained elements.
* @param keyExtractor function to extract a key from the contained elements.
* @param minimumCapacity the minimum and initial capacity of this priority queue.
* @param keyGroupRange the key-group range of the elements in this set.
* @param totalNumberOfKeyGroups the total number of key-groups of the job.
*/
@SuppressWarnings("unchecked")
public HeapPriorityQueueSet(
@Nonnull PriorityComparator elementPriorityComparator,
@Nonnull KeyExtractorFunction keyExtractor,
@Nonnegative int minimumCapacity,
@Nonnull KeyGroupRange keyGroupRange,
@Nonnegative int totalNumberOfKeyGroups) {
super(elementPriorityComparator, minimumCapacity);
this.keyExtractor = keyExtractor;
this.totalNumberOfKeyGroups = totalNumberOfKeyGroups;
this.keyGroupRange = keyGroupRange;
final int keyGroupsInLocalRange = keyGroupRange.getNumberOfKeyGroups();
final int deduplicationSetSize = 1 + minimumCapacity / keyGroupsInLocalRange;
this.deduplicationMapsByKeyGroup = new HashMap[keyGroupsInLocalRange];
for (int i = 0; i < keyGroupsInLocalRange; ++i) {
deduplicationMapsByKeyGroup[i] = new HashMap<>(deduplicationSetSize);
}
}
@Override
@Nullable
public T poll() {
final T toRemove = super.poll();
return toRemove != null ? getDedupMapForElement(toRemove).remove(toRemove) : null;
}
/**
* Adds the element to the queue. In contrast to the superclass and to maintain set semantics, this happens only if
* no such element is already contained (determined by {@link #equals(Object)}).
*
* @return true if the operation changed the head element or if is it unclear if the head element changed.
* Only returns false iff the head element was not changed by this operation.
*/
@Override
public boolean add(@Nonnull T element) {
return getDedupMapForElement(element).putIfAbsent(element, element) == null && super.add(element);
}
/**
* In contrast to the superclass and to maintain set semantics, removal here is based on comparing the given element
* via {@link #equals(Object)}.
*
* @return true if the operation changed the head element or if is it unclear if the head element changed.
* Only returns false iff the head element was not changed by this operation.
*/
@Override
public boolean remove(@Nonnull T toRemove) {
T storedElement = getDedupMapForElement(toRemove).remove(toRemove);
return storedElement != null && super.remove(storedElement);
}
@Override
public void clear() {
super.clear();
for (HashMap elementHashMap : deduplicationMapsByKeyGroup) {
elementHashMap.clear();
}
}
private HashMap getDedupMapForKeyGroup(
@Nonnegative int keyGroupId) {
return deduplicationMapsByKeyGroup[globalKeyGroupToLocalIndex(keyGroupId)];
}
private HashMap getDedupMapForElement(T element) {
int keyGroup = KeyGroupRangeAssignment.assignToKeyGroup(
keyExtractor.extractKeyFromElement(element),
totalNumberOfKeyGroups);
return getDedupMapForKeyGroup(keyGroup);
}
private int globalKeyGroupToLocalIndex(int keyGroup) {
checkArgument(keyGroupRange.contains(keyGroup), "%s does not contain key group %s", keyGroupRange, keyGroup);
return keyGroup - keyGroupRange.getStartKeyGroup();
}
@Nonnull
@Override
public Set getSubsetForKeyGroup(int keyGroupId) {
return getDedupMapForKeyGroup(keyGroupId).keySet();
}
}