/*
* 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.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 State {
/**
* Returns the current value associated with the given key.
*
* @param key The key of the mapping
* @return The value of the mapping with the given key
*
* @throws Exception Thrown if the system cannot access the state.
*/
UV get(UK key) throws Exception;
/**
* Associates a new value with the given key.
*
* @param key The key of the mapping
* @param value The new value of the mapping
*
* @throws Exception Thrown if the system cannot access the state.
*/
void put(UK key, UV value) throws Exception;
/**
* Copies all of the mappings from the given map into the state.
*
* @param map The mappings to be stored in this state
*
* @throws Exception Thrown if the system cannot access the state.
*/
void putAll(Map<UK, UV> map) throws Exception;
/**
* Deletes the mapping of the given key.
*
* @param key The key of the mapping
*
* @throws Exception Thrown if the system cannot access the state.
*/
void remove(UK key) throws Exception;
/**
* Returns whether there exists the given mapping.
*
* @param key The key of the mapping
* @return True if there exists a mapping whose key equals to the given key
*
* @throws Exception Thrown if the system cannot access the state.
*/
boolean contains(UK key) throws Exception;
/**
* Returns all the mappings in the state
*
* @return An iterable view of all the key-value pairs in the state.
*
* @throws Exception Thrown if the system cannot access the state.
*/
Iterable<Map.Entry<UK, UV>> entries() throws Exception;
/**
* Returns all the keys in the state
*
* @return An iterable view of all the keys in the state.
*
* @throws Exception Thrown if the system cannot access the state.
*/
Iterable<UK> keys() throws Exception;
/**
* Returns all the values in the state.
*
* @return An iterable view of all the values in the state.
*
* @throws Exception Thrown if the system cannot access the state.
*/
Iterable<UV> values() throws Exception;
/**
* Iterates over all the mappings in the state.
*
* @return An iterator over all the mappings in the state
*
* @throws Exception Thrown if the system cannot access the state.
*/
Iterator<Map.Entry<UK, UV>> iterator() throws Exception;
}