geode-core/src/main/java/org/apache/geode/cache/query/internal/SelectResultsComparator.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.geode.cache.query.internal;

import java.util.Comparator;
import java.util.Objects;

import org.apache.geode.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.
 *
 */

class SelectResultsComparator implements Comparator {

  /**
   * Sort the array in ascending order of collection sizes.
   */
  @Override
  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;
  }

  @Override
  public int hashCode() {
    return Objects.hash(this);
  }
}