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/*
 * Copyright (c) 2010-2015 Pivotal Software, Inc. All rights reserved.
 *
 * Licensed 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. See accompanying
 * LICENSE file.
 */
package com.gemstone.gemfire.cache.query.internal;

import java.util.Comparator;

import com.gemstone.gemfire.cache.query.SelectResults;

/**
 * Comparator used by the sorted set for storing the results obtained from
 * evaluation of various filter operands in an increasing order of the size ,
 * which will ensure that the intersection of the results for evaluation of AND
 * junction is optimum in performance.
 * 
 * @author ketan
 */

class SelectResultsComparator implements Comparator {

  /**
   * Sort the array in ascending order of collection sizes.
   */
  public int compare(Object obj1, Object obj2) {
    if (!(obj1 instanceof SelectResults) || !(obj2 instanceof SelectResults)) {
      Support.assertionFailed("The objects need to be of type SelectResults");
    }
    int answer = -1;
    SelectResults sr1 = (SelectResults) obj1;
    SelectResults sr2 = (SelectResults) obj2;
    int sizeDifference = sr1.size() - sr2.size();
    if (obj1 == obj2) {
      answer = 0;
    }
    else if (sizeDifference > 0) {
      answer = 1;
    }
    return answer;
  }

  /**
   * Overwrite default equals implementation.
   */
  @Override
  public boolean equals(Object o1) {
    return this == o1;
  }
}