org.apache.flink.runtime.state.subkeyed.SubKeyedValueState Maven / Gradle / Ivy

/*
 * 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.subkeyed;

import org.apache.flink.runtime.state.StateTransformationFunction;

/**
 * The interface for {@link SubKeyedState} whose values are single-values.
 *
 * @param  The type of the keys in the state.
 * @param  The type of the namespaces in the state.
 * @param  The type of the keys in the state.
 */
public interface SubKeyedValueState extends SubKeyedState {

	/**
	 * Associates the given value with the given key and namespace in the state.
	 * If there already exists a value under the given key and namespace, the
	 * value will be replaced with the given value.
	 *
	 * @param key The key under which the given value is to be associated.
	 * @param namespace The namespace of the value to be associated.
	 * @param value The value to be associated.
	 */
	void put(K key, N namespace, V value);

	/**
	 * Returns and removes the value under the given key and namespace in the state.
	 *
	 * @param key The key under which the value is to be retrieved.
	 * @param namespace The namespace of the value to be retrieved.
	 * @return The value under the given key and namespace in the state.
	 */
	V getAndRemove(K key, N namespace);

	/**
	 * Applies the given {@link StateTransformationFunction} to the state (1st input argument), using the given value as
	 * second input argument. The result of {@link StateTransformationFunction#apply(Object, Object)} is then stored as
	 * the new state. This function is basically an optimization for get-update-put pattern.
	 *
	 * @param key            the key.
	 * @param value          the value to use in transforming the state.
	 * @param namespace      the namespace.
	 * @param transformation the transformation function.
	 */
	 void transform(K key, N namespace, T value, StateTransformationFunction transformation);
}