/**
* 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.hadoop.hive.ql.exec;
import java.util.concurrent.Callable;
import java.util.concurrent.Future;
import org.apache.hadoop.hive.ql.metadata.HiveException;
/**
* ObjectCache. Interface for maintaining objects associated with a task.
*/
public interface ObjectCache {
/**
* @param key
*/
public void release(String key);
/**
* Retrieve object from cache.
*
* @param <T>
* @param key
* @param fn
* function to generate the object if it's not there
* @return the last cached object with the key, null if none.
*/
public <T> T retrieve(String key, Callable<T> fn) throws HiveException;
/**
* Retrieve object from cache.
*
* @param <T>
* @param key
* function to generate the object if it's not there
* @return the last cached object with the key, null if none.
*/
public <T> T retrieve(String key) throws HiveException;
/**
* Retrieve object from cache asynchronously.
*
* @param <T>
* @param key
* @param fn
* function to generate the object if it's not there
* @return the last cached object with the key, null if none.
*/
public <T> Future<T> retrieveAsync(String key, Callable<T> fn) throws HiveException;
/**
* Removes the specified key from the object cache.
*
* @param key - key to be removed
*/
public void remove(String key);
}