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Subject [GitHub] michaelandrepearce commented on a change in pull request #2548: ARTEMIS-2118 Enhanced Message Groups Support
Date Thu, 14 Feb 2019 08:19:32 GMT
michaelandrepearce commented on a change in pull request #2548: ARTEMIS-2118 Enhanced Message
Groups Support

 File path: artemis-commons/src/main/java/org/apache/activemq/artemis/utils/collections/
 @@ -0,0 +1,177 @@
+ * 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
+ *
+ *
+ *
+ * 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.activemq.artemis.utils.collections;
+import io.netty.util.collection.IntObjectHashMap;
+import io.netty.util.collection.IntObjectMap;
+import java.util.Collection;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.BiConsumer;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+ * BucketMap, stores values against a bucket, where the bucket used is based on the provided
key objects hash.
+ *
+ * As such where keys compute to the same bucket they will act on that stored value, not
the unique specific keys as you'd normally expect from a map.
+ *
+ * The number of buckets is provided at construction.
+ *
+ * Its initial use, is in QueueImpl, where we want to bucket message groups to consumers.
+ *
+ * @param <K> the key type.
+ * @param <V> the value type.
+ */
+public class BucketMap<K, V> implements Map<K, V> {
+   private final IntObjectMap<V> buckets = new IntObjectHashMap<>();
 Review comment:
   Collisions are 100% expected we are bucketing. E.g if bucket size is two and the key was
integer with keys 1 and 3 i actually expect them to collide and goto the same bucket. Like
wise if someone uses a non power of 2 bucket count that should be honored, e.g. say 5 buckets
was set, then we must only have use 5 buckets, not the next power of 2 buckets.
   Re map vs array, i was toying on the same thing, downside with array is up front will need
to allocate the memory for that array even if not all buckets used. Benefit of using underlying
map is it will grow as needed.
   Also codally its cleaner as simply we hash mod the key and then delegate method to underlying

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