autumnust commented on a change in pull request #651: URL: https://github.com/apache/orc/pull/651#discussion_r613598496
########## File path: java/core/src/java/org/apache/orc/impl/StringHashTableDictionary.java ########## @@ -0,0 +1,189 @@ +/* + * 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.orc.impl; + +import java.io.IOException; +import java.util.Arrays; + +import org.apache.hadoop.io.Text; + + +/** + * Using HashTable to represent a dictionary. The strings are stored as UTF-8 bytes + * and an offset for each entry. It is using chaining for collision resolution. + * + * This implementation is not thread-safe. It also assumes there's no reduction in the size of hash-table + * as it shouldn't happen in the use cases for this class. + */ +public class StringHashTableDictionary implements Dictionary { + + private final DynamicByteArray byteArray = new DynamicByteArray(); + // starting offset of key-in-byte in the byte array for the i-th key. + // Two things combined stores the key array. + private final DynamicIntArray keyOffsets; + + private final Text newKey = new Text(); + + private DynamicIntArray[] hashArray; Review comment: Let me wrap up the benchmark for this version and we could then compare the linear-probing approach. But yeah I agree that linear probing seems more promising. -- 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. For queries about this service, please contact Infrastructure at: [email protected]
