org.apache.flink.runtime.state.StateStorage Maven / Gradle / Ivy
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* 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;
import org.apache.flink.types.Pair;
/**
* Interface for State Storage, State storage is a Key/Value store that
* stores all the states.
*
* @param Type of key that will be stored to the current storage.
* @param Type of value that will be stored to the current storage.
*/
public interface StateStorage {
/**
* Associates the given value with the given key in the storage.
* If the storage previously contains a value for the given key,
* the old value will be replaced with the new value.
*
* @param key The key with which the given value is to be associated.
* @param value The value to be associated with the given key.
*
* @throws Exception The method may forward exception thrown internally (by I/O or functions).
*/
void put(K key, V value) throws Exception;
/**
* Returns the value associated with the given key in the state.
* Null will be returned if this state contains no value for the key.
*
* @param key The key of the value to be retrieved.
* @return The value associated with the given key.
*
* @throws Exception Thrown if the system cannot access the value from storage.
*/
V get(K key) throws Exception;
/**
* Removes the value for the given key from the storage if it is present.
*
* @param key The key of the value to be removed.
* @return true if remove successfully.
*
* @throws Exception The method may forward exception thrown internally (by I/O or functions).
*/
boolean remove(K key) throws Exception;
/**
* Returns an iterator over all the key-values in the storage. There are no
* guarantees concerning the order in which the key-values are iterated.
*
* @return An iterator over all the key-values in the state.
*
* @throws Exception Thrown if the system cannot access the state.
*/
StorageIterator iterator() throws Exception;
/**
* Returns an iterator over all the key-values whose key with the prefix {@code prefixKey} in the storage.
* There are no guarantees concerning the order in which the key-values are iterated.
*
* @return An iterator over all the key-values in the state.
*
* @throws Exception Thrown if the system cannot access the state.
*/
StorageIterator prefixIterator(K prefixKey) throws Exception;
/**
* Returns an iterator over all the key-values whose key locates in the range of {@code prefixKeyStart} and {@code prefixKeyEnd}.
*
* @param prefixKeyStart The start key of the sub Iterator.
* @param prefixKeyEnd The end key of the sub Iterator.
*
* @return An iterator over all the key-values in the state.
*
* @throws UnsupportedOperationException if the storage is not sorted.
* @throws Exception Thrown if the system cannot access the state.
*/
StorageIterator subIterator(K prefixKeyStart, K prefixKeyEnd) throws Exception;
/**
* Returns the first entry in the storage whose key is large than specified key.
*
* @param specifiedKey The specified key used to retrieved the first entry.
*
* @return The entry in the storage whose key is smallest among the entries
* with the same prefix.
*
* @throws UnsupportedOperationException if the storage is not sorted.
*
*/
Pair firstEntry(K specifiedKey);
/**
* Returns the last entry in the storage whose key is no larger than the given specified key.
*
* @param specifiedKey The specified key to retrieve the last entry.
*
* @return The last entry in the storage whose key is no larger than the given specified key.
*
* @throws UnsupportedOperationException if the storage is not sorted.
*/
Pair lastEntry(K specifiedKey);
/**
* Merge the given value to exist value of the given key. If the state didn't
* previously contains a value for the given key, the result will be the given value.
*
* @param key The key with which the given value is to be merged to.
* @param value The value to be merged to the given key.
*
* @throws Exception The method may forward exception thrown internally (by I/O or functions).
*/
void merge(K key, V value) throws Exception;
/**
* Returns whether the key/value need to be (de)serialized when put to the storage,
* or get from the storage.
*
* @return false for need (de)serialize before put to/get from the storage.
*/
boolean lazySerde();
/**
* Whether the storage support multi column family.
*
* @return true for the storage supports multi column family.
*/
boolean supportMultiColumnFamilies();
/**
* Returns the StorageInstance associated with the storage.
*
* @return The storageInstance associated with the storage.
*/
StorageInstance getStorageInstance();
}