ankitsultana commented on code in PR #16242: URL: https://github.com/apache/pinot/pull/16242#discussion_r2181161175
########## pinot-query-planner/src/main/java/org/apache/pinot/query/planner/partitioning/HashFunctionSelector.java: ########## @@ -0,0 +1,119 @@ +/** + * 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.query.planner.partitioning; + +import java.nio.charset.StandardCharsets; +import org.apache.pinot.spi.utils.hash.CityHashFunctions; +import org.apache.pinot.spi.utils.hash.MurmurHashFunctions; + + +/** + * Utility class to compute hash values using different hash functions. + * This class provides consistent hash computation for KeySelector implementations. + */ +public class HashFunctionSelector { + public static final String MURMUR2 = "murmur2"; + public static final String MURMUR3 = "murmur3"; + public static final String CITY_HASH = "cityhash"; + public static final String ABS_HASH_CODE = "absHashCode"; + + private HashFunctionSelector() { + } + + /** + * Computes a hash code for a single value using the specified hash function. + * @param value The value to hash. + * @param hashFunction The hash function to use (e.g., "murmur2", "murmur3", "cityhash", "absHashCode"). + * @return The computed hash code. + */ + public static int computeHash(Object value, String hashFunction) { + if (value == null) { + return 0; + } + + switch (hashFunction.toLowerCase()) { + case MURMUR2: return murmur2(value); + case MURMUR3: return murmur3(value); + case CITY_HASH: return cityHash(value); + // Default hash is absHashCode. + default: return absHashCode(value); + } + } + + /** + * Computes a hash code for multiple values using the specified hash function. + * @param values The array of values to hash. + * @param hashFunction The hash function to use (e.g., "murmur2", "murmur3", "cityhash", "absHashCode"). + * @return The computed hash code. + */ + public static int computeMultiHash(Object[] values, String hashFunction) { + if (values == null || values.length == 0) { + return 0; + } + + switch (hashFunction.toLowerCase()) { + case MURMUR2: return multiHash(values, HashFunctionSelector::murmur2); + case MURMUR3: return multiHash(values, HashFunctionSelector::murmur3); + case CITY_HASH: return multiHash(values, HashFunctionSelector::cityHash); + // Default hash is absHashCode. + default: return multiAbsHashCode(values); + } + } + + private static int absHashCode(Object value) { + return value.hashCode() & Integer.MAX_VALUE; + } + + // multiAbsHashCode is different from absHashCode due to legacy implementation. + private static int multiAbsHashCode(Object[] values) { + int hash = 0; + for (Object value : values) { + if (value != null) { + hash += value.hashCode(); + } + } + return hash & Integer.MAX_VALUE; + } + + private static int murmur2(Object value) { Review Comment: I think we should delegate to `PartitionFunctionFactory`? -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: commits-unsubscr...@pinot.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: commits-unsubscr...@pinot.apache.org For additional commands, e-mail: commits-h...@pinot.apache.org
