org.apache.flink.runtime.state.heap.TreeOrderedSetCache Maven / Gradle / Ivy
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* to you under the Apache License, Version 2.0 (the
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* 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 it.unimi.dsi.fastutil.objects.ObjectAVLTreeSet;
import org.apache.flink.util.CloseableIterator;
import org.apache.flink.util.Preconditions;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import java.util.Comparator;
/**
* Implementation of {@link org.apache.flink.runtime.state.heap.CachingInternalPriorityQueueSet.OrderedSetCache} based
* on an AVL-Tree. We chose the implementation from fastutil over JDK for performance reasons.
*
* Maintainer notes: We can consider the following potential performance improvements. First, we could introduce a
* bulk-load method to OrderedSetCache to exploit the fact that adding from an OrderedSetStore is already happening in
* sorted order, e.g. there are more efficient ways to construct search trees from sorted elements. Second, we could
* replace the internal AVL-Tree with an extended variant of {@link HeapPriorityQueueSet} that is organized as a
* Min-Max-Heap.
*
* @param type of the contained elements.
*/
public class TreeOrderedSetCache implements CachingInternalPriorityQueueSet.OrderedSetCache {
//TODO: use [FLINK-9981] to optimize the performance.
/** The tree is used to store cached elements. */
@Nonnull
private final ObjectAVLTreeSet avlTree;
/** The element comparator. */
@Nonnull
private final Comparator elementComparator;
/** The maximum capacity of the cache. */
@Nonnegative
private final int capacity;
/**
* Creates a new {@link TreeOrderedSetCache} with the given capacity and element comparator. Capacity must be > 0.
* @param elementComparator comparator for the cached elements.
* @param capacity the capacity of the cache. Must be > 0.
*/
public TreeOrderedSetCache(@Nonnull Comparator elementComparator, @Nonnegative int capacity) {
Preconditions.checkArgument(capacity > 0, "Cache capacity must be greater than 0.");
this.avlTree = new ObjectAVLTreeSet<>(elementComparator);
this.elementComparator = elementComparator;
this.capacity = capacity;
}
@Override
public void add(@Nonnull E element) {
assert !isFull();
avlTree.add(element);
}
@Override
public void remove(@Nonnull E element) {
avlTree.remove(element);
}
@Override
public boolean isFull() {
return avlTree.size() == capacity;
}
@Override
public boolean isEmpty() {
return avlTree.isEmpty();
}
@Override
public boolean isInLowerBound(@Nonnull E toCheck) {
return avlTree.isEmpty() || elementComparator.compare(peekLast(), toCheck) > 0;
}
@Nullable
@Override
public E removeFirst() {
if (avlTree.isEmpty()) {
return null;
}
final E first = avlTree.first();
avlTree.remove(first);
return first;
}
@Nullable
@Override
public E removeLast() {
if (avlTree.isEmpty()) {
return null;
}
final E last = avlTree.last();
avlTree.remove(last);
return last;
}
@Nullable
@Override
public E peekFirst() {
return !avlTree.isEmpty() ? avlTree.first() : null;
}
@Nullable
@Override
public E peekLast() {
return !avlTree.isEmpty() ? avlTree.last() : null;
}
@Nonnull
@Override
public CloseableIterator orderedIterator() {
return CloseableIterator.adapterForIterator(avlTree.iterator());
}
}