heyihong commented on code in PR #53625: URL: https://github.com/apache/spark/pull/53625#discussion_r2651885552
########## common/utils-java/src/main/java/org/apache/spark/util/UUIDv7Generator.java: ########## @@ -0,0 +1,74 @@ +/* + * 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.spark.util; + +import java.time.Instant; +import java.util.UUID; +import java.util.concurrent.ThreadLocalRandom; + +/** + * Generator for UUIDv7 as defined in + * https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format#section-5.2 + * + * UUIDv7 is a time-ordered UUID that embeds a Unix timestamp in milliseconds, + * making it suitable for use as database keys and for cases where temporal + * ordering is beneficial. + */ +public final class UUIDv7Generator { + + private UUIDv7Generator() { + // Prevent instantiation + } + + /** + * Generate a UUIDv7 from the current time. + * + * @return a new UUIDv7 + */ + public static UUID generate() { Review Comment: @asl3 I am not sure whether the current implementation meets the requirements of UUIDv7. Based on [Section 6.2](https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format#section-6.2) of the specification: ``` Monotonicity is the backbone of time-based sortable UUIDs. Naturally time-based UUIDs from this document will be monotonic due to an embedded timestamp however implementations can guarantee additional monotonicity via the concepts covered in this section. ``` However, the current implementation does not guarantee monotonicity because `Instant.now()` is not monotonically increasing. -- 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]
