content: /*
   * 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.carbondata.processing.loading.sort;
  
  import java.lang.reflect.Field;
  import java.lang.reflect.Method;
  import java.util.Comparator;
  import java.util.PriorityQueue;
  
  import org.apache.carbondata.processing.loading.exception.CarbonDataLoadingException;
  
  /**
   * This class is used to optimize sort step performance while getting row from heap,
   * including intermediate merge and final sort merge in loading process,
   * by accessing member/method in PriorityQueue
   */
  public class CarbonPriorityQueue<E> extends PriorityQueue<E> {
    private transient Field queueField;
    private transient Method siftDownMethod;
    private static final long serialVersionUID = 1L;
  
    public CarbonPriorityQueue(int initialCapacity) {
      super(initialCapacity);
      init();
    }
  
    public CarbonPriorityQueue(int initialCapacity, Comparator<? super E> comparator) {
      super(initialCapacity, comparator);
      init();
    }
  
    private void init() {
      try {
        queueField = PriorityQueue.class.getDeclaredField("queue");
        queueField.setAccessible(true);
        siftDownMethod = PriorityQueue.class.getDeclaredMethod("siftDown", int.class, Object.class);
        siftDownMethod.setAccessible(true);
      } catch (ReflectiveOperationException e) {
        throw new CarbonDataLoadingException("Reflective operation failed", e);
      }
    }
  
    public void siftTopDown() {
      try {
        Object topNode = ((Object[]) queueField.get(this))[0];
        siftDownMethod.invoke(this, 0, topNode);
      } catch (ReflectiveOperationException e) {
        throw new CarbonDataLoadingException("Reflective operation failed", e);
      }
    }
  }
  