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https://issues.apache.org/jira/browse/FLINK-9423?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16495077#comment-16495077
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ASF GitHub Bot commented on FLINK-9423:
---------------------------------------
Github user StefanRRichter commented on a diff in the pull request:
https://github.com/apache/flink/pull/6062#discussion_r191738639
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/InternalTimerHeap.java
---
@@ -0,0 +1,511 @@
+/*
+ * 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.flink.streaming.api.operators;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.runtime.state.KeyGroupRange;
+import org.apache.flink.runtime.state.KeyGroupRangeAssignment;
+
+import javax.annotation.Nonnegative;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.Queue;
+import java.util.Set;
+
+import static org.apache.flink.util.Preconditions.checkArgument;
+
+/**
+ * A heap-based priority queue for internal timers. This heap is supported
by hash sets for fast contains
+ * (de-duplication) and deletes. The heap implementation is a simple
binary tree stored inside an array. Element indexes
+ * in the heap array start at 1 instead of 0 to make array index
computations a bit simpler in the hot methods.
+ *
+ * <p>Possible future improvements:
+ * <ul>
+ * <li>We could also implement shrinking for the heap and the
deduplication maps.</li>
+ * <li>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..</li>
+ * </ul>
+ *
+ * @param <K> type of the key of the internal timers managed by this
priority queue.
+ * @param <N> type of the namespace of the internal timers managed by this
priority queue.
+ */
+public class InternalTimerHeap<K, N> implements
Queue<TimerHeapInternalTimer<K, N>>, Set<TimerHeapInternalTimer<K, N>> {
--- End diff --
I think `toArray` (for later snapshots) and `iterator` (for tests and in
general) are actually useful. Will consider removing the interfaces.
> Implement efficient deletes for heap based timer service
> --------------------------------------------------------
>
> Key: FLINK-9423
> URL: https://issues.apache.org/jira/browse/FLINK-9423
> Project: Flink
> Issue Type: Improvement
> Components: Streaming
> Affects Versions: 1.5.0
> Reporter: Stefan Richter
> Assignee: Stefan Richter
> Priority: Major
> Fix For: 1.6.0
>
>
> The current data structures in the `HeapInternalTimerService` are not able to
> support efficient timer deletes, the complexity is currently O\(n\), where n
> is the number of registered timers.
>
> We can keep track of timer's positions in the priority queue and (in
> combination with the already existing set/map) have a more efficient
> algorithm for deletes.
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