/*
* 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.streaming.api.windowing.assigners;
import java.util.Collection;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.streaming.api.windowing.windows.Window;
/**
* A {@code WindowAssigner} that can merge windows.
*
* @param <T> The type of elements that this WindowAssigner can assign windows to.
* @param <W> The type of {@code Window} that this assigner assigns.
*/
@PublicEvolving
public abstract class MergingWindowAssigner<T, W extends Window> extends WindowAssigner<T, W> {
private static final long serialVersionUID = 1L;
/**
* Determines which windows (if any) should be merged.
*
* @param windows The window candidates.
* @param callback A callback that can be invoked to signal which windows should be merged.
*/
public abstract void mergeWindows(Collection<W> windows, MergeCallback<W> callback);
/**
* Callback to be used in {@link #mergeWindows(Collection, MergeCallback)} for specifying which
* windows should be merged.
*/
public interface MergeCallback<W> {
/**
* Specifies that the given windows should be merged into the result window.
*
* @param toBeMerged The list of windows that should be merged into one window.
* @param mergeResult The resulting merged window.
*/
void merge(Collection<W> toBeMerged, W mergeResult);
}
}