com.google.appengine.api.datastore.BaseQuerySplitter Maven / Gradle / Ivy

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/*
 * Copyright 2021 Google LLC
 *
 * 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
 *
 *     https://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 com.google.appengine.api.datastore;

import com.google.appengine.api.datastore.Query.SortDirection;
import java.util.Collections;
import java.util.Comparator;

/**
 * Base implementation of {@link QuerySplitter} with logic common to all splitters.
 *
 */
abstract class BaseQuerySplitter implements QuerySplitter {
  protected static final Comparator VALUE_COMPARATOR_ASC =
      new Comparator() {
        @Override
        public int compare(ComparableValue o1, ComparableValue o2) {
          return EntityProtoComparators.MULTI_TYPE_COMPARATOR.compare(
              o1.comparableValue, o2.comparableValue);
        }
      };

  protected static final Comparator VALUE_COMPARATOR_DESC =
      Collections.reverseOrder(VALUE_COMPARATOR_ASC);

  protected BaseQuerySplitter() {}

  /**
   * A class that allows arbitrary property values to be compared while preserving their original
   * value.
   *
   * This is needed because converting a value into a {@code Comparable