Github user sihuazhou commented on a diff in the pull request:
https://github.com/apache/flink/pull/6228#discussion_r199320135
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/state/heap/CachingInternalPriorityQueueSet.java
---
@@ -0,0 +1,288 @@
+/*
+ * 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.runtime.state.heap;
+
+import org.apache.flink.runtime.state.InternalPriorityQueue;
+import org.apache.flink.util.CloseableIterator;
+import org.apache.flink.util.FlinkRuntimeException;
+
+import javax.annotation.Nonnegative;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+
+import java.util.Collection;
+
+/**
+ * This class is an implementation of a {@link InternalPriorityQueue} with
set semantics that internally consists of
+ * two different storage types. The first storage is a (potentially slow)
ordered set store manages the ground truth
+ * about the elements in this queue. The second storage is a (fast)
ordered set cache, typically with some limited
+ * capacity. The cache is used to improve performance of accesses to the
underlying store and contains contains an
--- End diff --
duplicated `contains`
---
