gianm commented on code in PR #12277: URL: https://github.com/apache/druid/pull/12277#discussion_r1005089652
########## processing/src/main/java/org/apache/druid/segment/column/StringEncodingStrategies.java: ########## @@ -0,0 +1,126 @@ +/* + * 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.druid.segment.column; + +import org.apache.druid.java.util.common.ISE; +import org.apache.druid.java.util.common.StringUtils; +import org.apache.druid.query.monomorphicprocessing.RuntimeShapeInspector; +import org.apache.druid.segment.data.DictionaryWriter; +import org.apache.druid.segment.data.EncodedStringDictionaryWriter; +import org.apache.druid.segment.data.FrontCodedIndexedWriter; +import org.apache.druid.segment.data.GenericIndexed; +import org.apache.druid.segment.data.GenericIndexedWriter; +import org.apache.druid.segment.data.Indexed; +import org.apache.druid.segment.writeout.SegmentWriteOutMedium; + +import javax.annotation.Nullable; +import java.nio.ByteBuffer; +import java.nio.ByteOrder; +import java.util.Iterator; + +public class StringEncodingStrategies +{ + public static DictionaryWriter<String> getStringDictionaryWriter( + StringEncodingStrategy encodingStrategy, + SegmentWriteOutMedium writeoutMedium, + String fileName + ) + { + // write plain utf8 in the legacy format, where generic indexed was written directly + if (StringEncodingStrategy.UTF8.equals(encodingStrategy.getType())) { + return new GenericIndexedWriter<>(writeoutMedium, fileName, GenericIndexed.STRING_STRATEGY); + } else { + // otherwise, we wrap in an EncodedStringDictionaryWriter so that we write a small header that includes + // a version byte that should hopefully never conflict with a GenericIndexed version, along with a byte + // from StringEncodingStrategy.getId to indicate which encoding strategy is used for the dictionary before + // writing the dictionary itself + DictionaryWriter<byte[]> writer; + if (StringEncodingStrategy.FRONT_CODED.equals(encodingStrategy.getType())) { + writer = new FrontCodedIndexedWriter( + writeoutMedium, + ByteOrder.nativeOrder(), Review Comment: What I'm suggesting is we should use little-endian ordering even on big-endian architectures, because it's important that the segment format be well-specified. (Otherwise, if you switch your cluster to CPUs with a different architecture, the new servers won't be able to read the old segments.) If this was already a problem that you're just inheriting, I guess it's okay and you don't have to do anything about it right now. -- 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: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
