vcrfxia commented on code in PR #13188: URL: https://github.com/apache/kafka/pull/13188#discussion_r1101882173
########## streams/src/main/java/org/apache/kafka/streams/state/VersionedKeyValueStore.java: ########## @@ -0,0 +1,99 @@ +/* + * 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.kafka.streams.state; + +import org.apache.kafka.streams.errors.InvalidStateStoreException; +import org.apache.kafka.streams.processor.StateStore; + +/** + * A key-value store that stores multiple record versions per key, and supports timestamp-based + * retrieval operations to return the latest record (per key) as of a specified timestamp. + * Only one record is stored per key and timestamp, i.e., a second call to + * {@link #put(Object, Object, long)} with the same key and timestamp will replace the first. + * <p> + * Each store instance has an associated, fixed-duration "history retention" which specifies + * how long old record versions should be kept for. In particular, a versioned store guarantees + * to return accurate results for calls to {@link #get(Object, long)} where the provided timestamp + * bound is within history retention of the current observed stream time. (Queries with timestamp + * bound older than the specified history retention are considered invalid.) + * + * @param <K> The key type + * @param <V> The value type + */ +public interface VersionedKeyValueStore<K, V> extends StateStore { + + /** + * Add a new record version associated with this key. + * + * @param key The key + * @param value The value, it can be {@code null}; + * if the serialized bytes are also {@code null} it is interpreted as a delete Review Comment: Hm... I found this [comment](https://github.com/apache/kafka/blob/083e11a22ca9966ed010acdd5705351ab4300b52/streams/src/main/java/org/apache/kafka/streams/state/internals/ValueAndTimestampSerializer.java#L87-L89) in the code the other day, which gives the impression that it is valid to serialize a non-null value to null bytes: > // Serializing non-null values to null can be useful when working with Optional-like values > // where the Optional.empty case is serialized to null. > // See the discussion here: https://github.com/apache/kafka/pull/7679 Is this no longer true? -- 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: jira-unsubscr...@kafka.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
