/*
* 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.runtime.state.internal;
import org.apache.flink.api.common.state.State;
/**
* The {@code InternalKvState} is the root of the internal state type hierarchy, similar to the
* {@link State} being the root of the public API state hierarchy.
*
* <p>The internal state classes give access to the namespace getters and setters and access to
* additional functionality, like raw value access or state merging.
*
* <p>The public API state hierarchy is intended to be programmed against by Flink applications.
* The internal state hierarchy holds all the auxiliary methods that are used by the runtime and not
* intended to be used by user applications. These internal methods are considered of limited use to users and
* only confusing, and are usually not regarded as stable across releases.
*
* <p>Each specific type in the internal state hierarchy extends the type from the public
* state hierarchy:
*
* <pre>
* State
* |
* +-------------------InternalKvState
* | |
* MergingState |
* | |
* +-----------------InternalMergingState
* | |
* +--------+------+ |
* | | |
* ReducingState ListState +-----+-----------------+
* | | | |
* +-----------+ +----------- -----------------InternalListState
* | |
* +---------InternalReducingState
* </pre>
*
* @param <N> The type of the namespace.
*/
public interface InternalKvState<N> extends State {
/**
* Sets the current namespace, which will be used when using the state access methods.
*
* @param namespace The namespace.
*/
void setCurrentNamespace(N namespace);
/**
* Returns the serialized value for the given key and namespace.
*
* <p>If no value is associated with key and namespace, <code>null</code>
* is returned.
*
* @param serializedKeyAndNamespace Serialized key and namespace
* @return Serialized value or <code>null</code> if no value is associated with the key and namespace.
*
* @throws Exception Exceptions during serialization are forwarded
*/
byte[] getSerializedValue(byte[] serializedKeyAndNamespace) throws Exception;
}