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Posted to commits@pinot.apache.org by "snleee (via GitHub)" <gi...@apache.org> on 2023/11/27 19:16:25 UTC
Re: [PR] Add support for murmur3 as a partition function [pinot]
snleee commented on code in PR #12049:
URL: https://github.com/apache/pinot/pull/12049#discussion_r1406592721
##########
pinot-segment-spi/src/main/java/org/apache/pinot/segment/spi/partition/Murmur3PartitionFunction.java:
##########
@@ -0,0 +1,69 @@
+/**
+ * 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.pinot.segment.spi.partition;
+
+import com.google.common.base.Preconditions;
+import com.google.common.hash.Hashing;
+import java.util.Map;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+
+/**
+ * Implementation of {@link PartitionFunction} which partitions based on 32 bit murmur3 hash
+ */
+public class Murmur3PartitionFunction implements PartitionFunction {
+ private static final String NAME = "Murmur3";
+ private final int _numPartitions;
+ private final int _hashSeed;
+
+ /**
+ * Constructor for the class.
+ * @param numPartitions Number of partitions.
+ * @param functionConfig to extract configurations for the partition function.
+ */
+ public Murmur3PartitionFunction(int numPartitions, Map<String, String> functionConfig) {
+ Preconditions.checkArgument(numPartitions > 0, "Number of partitions must be > 0");
+ _numPartitions = numPartitions;
+ _hashSeed = (functionConfig == null || functionConfig.get("seed") == null) ? 0
Review Comment:
seed = 0 is the default value for murmur3?
Apache commons uses the default seed value of `104729`?
https://commons.apache.org/proper/commons-codec/apidocs/org/apache/commons/codec/digest/MurmurHash3.html#DEFAULT_SEED
On the other hand, google's murmur3 hash function uses seed = 0 by default. Can we do a bit more research on this and make the informed decision?
##########
pinot-segment-spi/src/main/java/org/apache/pinot/segment/spi/partition/Murmur3PartitionFunction.java:
##########
@@ -0,0 +1,69 @@
+/**
+ * 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.pinot.segment.spi.partition;
+
+import com.google.common.base.Preconditions;
+import com.google.common.hash.Hashing;
+import java.util.Map;
+
+import static java.nio.charset.StandardCharsets.UTF_8;
+
+
+/**
+ * Implementation of {@link PartitionFunction} which partitions based on 32 bit murmur3 hash
+ */
+public class Murmur3PartitionFunction implements PartitionFunction {
+ private static final String NAME = "Murmur3";
+ private final int _numPartitions;
+ private final int _hashSeed;
+
+ /**
+ * Constructor for the class.
+ * @param numPartitions Number of partitions.
+ * @param functionConfig to extract configurations for the partition function.
+ */
+ public Murmur3PartitionFunction(int numPartitions, Map<String, String> functionConfig) {
+ Preconditions.checkArgument(numPartitions > 0, "Number of partitions must be > 0");
+ _numPartitions = numPartitions;
+ _hashSeed = (functionConfig == null || functionConfig.get("seed") == null) ? 0
+ : Integer.parseInt(functionConfig.get("seed"));
+ }
+
+ @Override
+ public int getPartition(Object value) {
+ return (Hashing.murmur3_32_fixed(_hashSeed).hashBytes(value.toString().getBytes(UTF_8)).asInt() & Integer.MAX_VALUE)
Review Comment:
it looks that murmur3 has `murmur3_32 / murmur3_128`. Can we add `TODO` comment to add 128 bit support when needed in the future?
##########
pinot-segment-spi/src/test/java/org/apache/pinot/segment/spi/partition/PartitionFunctionTest.java:
##########
@@ -115,6 +115,82 @@ public void testMurmurPartitioner() {
}
}
+ /**
+ * Unit test for {@link Murmur3PartitionFunction}.
+ * <ul>
+ * <li> Tests that partition values are in expected range. </li>
+ * <li> Tests that toString returns expected string. </li>
+ * <li> Tests that the partition numbers returned by partition function with null functionConfig and
+ * functionConfig with empty seed value are equal</li>
+ * </ul>
+ */
+ @Test
+ public void testMurmur3Partitioner() {
Review Comment:
Should we add the test comparing against some hand computed values?
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