[ https://issues.apache.org/jira/browse/FLINK-4856?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15874325#comment-15874325 ]
ASF GitHub Bot commented on FLINK-4856: --------------------------------------- Github user shixiaogang commented on a diff in the pull request: https://github.com/apache/flink/pull/3336#discussion_r101987352 --- Diff: flink-core/src/main/java/org/apache/flink/api/common/state/MapState.java --- @@ -0,0 +1,111 @@ +/* + * 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.flink.api.common.state; + +import org.apache.flink.annotation.PublicEvolving; + +import java.io.IOException; +import java.util.Iterator; +import java.util.Map; + +/** + * {@link State} interface for partitioned key-value state. The key-value pair can be + * added, updated and retrieved. + * + * <p>The state is accessed and modified by user functions, and checkpointed consistently + * by the system as part of the distributed snapshots. + * + * <p>The state is only accessible by functions applied on a KeyedDataStream. The key is + * automatically supplied by the system, so the function always sees the value mapped to the + * key of the current element. That way, the system can handle stream and state partitioning + * consistently together. + * + * @param <UK> Type of the keys in the state. + * @param <UV> Type of the values in the state. + */ +@PublicEvolving +public interface MapState<UK, UV> extends AppendingState<Map<UK, UV>, Iterable<Map.Entry<UK, UV>>> { --- End diff -- I agree that it's `MultiMapState`, instead of `MapState`, that is supposed to be an `AppendingState`. I will update the interface hierarchy, making `MapState` not an `AppendingState`. > Add MapState for keyed streams > ------------------------------ > > Key: FLINK-4856 > URL: https://issues.apache.org/jira/browse/FLINK-4856 > Project: Flink > Issue Type: New Feature > Components: DataStream API, State Backends, Checkpointing > Reporter: Xiaogang Shi > Assignee: Xiaogang Shi > > Many states in keyed streams are organized as key-value pairs. Currently, > these states are implemented by storing the entire map into a ValueState or a > ListState. The implementation however is very costly because all entries have > to be serialized/deserialized when updating a single entry. To improve the > efficiency of these states, MapStates are urgently needed. -- This message was sent by Atlassian JIRA (v6.3.15#6346)