/*
* 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.beam.runners.core;
import java.util.Map;
import org.apache.beam.sdk.annotations.Experimental;
import org.apache.beam.sdk.annotations.Experimental.Kind;
import org.apache.beam.sdk.state.State;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
/**
* Interface for accessing persistent state while windows are merging.
*
* <p>For internal use only.
*/
@Experimental(Kind.STATE)
public interface MergingStateAccessor<K, W extends BoundedWindow>
extends StateAccessor<K> {
/**
* Analogous to {@link #access}, but returned as a map from each window which is
* about to be merged to the corresponding state. Only includes windows which
* are known to have state.
*/
<StateT extends State> Map<W, StateT> accessInEachMergingWindow(
StateTag<StateT> address);
}