library/src/main/java/org/apache/apex/malhar/lib/window/impl/InMemoryWindowedKeyedStorage.java

/**
 * 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.apex.malhar.lib.window.impl;

import java.util.AbstractMap;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.apex.malhar.lib.state.spillable.Spillable;
import org.apache.apex.malhar.lib.window.SessionWindowedStorage;
import org.apache.apex.malhar.lib.window.Window;
import org.apache.apex.malhar.lib.window.WindowedKeyedStorage;
import org.apache.hadoop.classification.InterfaceStability;

/**
 * This is the in-memory implementation of {@link WindowedKeyedStorage}. Do not use this class if you have a large state that
 * can't be fit in memory. Also, this class may go away soon as there are plans to incorporate {@link Spillable} data structures
 * in the near future.
 *
 * @since 3.5.0
 */
@InterfaceStability.Unstable
public class InMemoryWindowedKeyedStorage<K, V> extends InMemoryWindowedStorage<Map<K, V>>
    implements WindowedKeyedStorage<K, V>, SessionWindowedStorage<K, V>
{
  @Override
  public void put(Window window, K key, V value)
  {
    Map<K, V> kvMap;
    if (map.containsKey(window)) {
      kvMap = map.get(window);
    } else {
      kvMap = new HashMap<K, V>();
      map.put(window, kvMap);
    }
    kvMap.put(key, value);
  }

  @Override
  public Set<Map.Entry<K, V>> entrySet(Window window)
  {
    if (map.containsKey(window)) {
      return map.get(window).entrySet();
    } else {
      return Collections.emptySet();
    }
  }

  @Override
  public V get(Window window, K key)
  {
    if (map.containsKey(window)) {
      return map.get(window).get(key);
    } else {
      return null;
    }
  }

  @Override
  public Collection<Map.Entry<Window.SessionWindow<K>, V>> getSessionEntries(K key, long timestamp, long gap)
  {
    List<Map.Entry<Window.SessionWindow<K>, V>> results = new ArrayList<>();
    // TODO: this is inefficient, but this is usually not used in a real use case since it's in memory
    for (Map.Entry<Window, Map<K, V>> entry : map.entrySet()) {
      Window.SessionWindow<K> window = (Window.SessionWindow<K>)entry.getKey();
      if (key.equals(window.getKey())) {
        if (timestamp > window.getBeginTimestamp()) {
          if (window.getBeginTimestamp() + window.getDurationMillis() + gap > timestamp) {
            results.add(new AbstractMap.SimpleEntry<>(window, entry.getValue().get(key)));
          }
        } else if (timestamp < window.getBeginTimestamp()) {
          if (window.getBeginTimestamp() - gap <= timestamp) {
            results.add(new AbstractMap.SimpleEntry<>(window, entry.getValue().get(key)));
          }
        } else {
          results.add(new AbstractMap.SimpleEntry<>(window, entry.getValue().get(key)));
        }
      }
    }
    return results;
  }
}