modules/core/src/main/java/org/apache/ignite/configuration/CheckpointWriteOrder.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.ignite.configuration;

import org.jetbrains.annotations.Nullable;

/**
 * This enum defines order of writing pages to disk storage during checkpoint.
 */
public enum CheckpointWriteOrder {
    /**
     * Pages are written in order provided by checkpoint pages collection iterator (which is basically a hashtable).
     */
    RANDOM,

    /**
     * All checkpoint pages are collected into single list and sorted by page index.
     * Provides almost sequential disk writes, which can be much faster on some SSD models.
     */
    SEQUENTIAL;

    /**
     * Enumerated values.
     */
    private static final CheckpointWriteOrder[] VALS = values();

    /**
     * Efficiently gets enumerated value from its ordinal.
     *
     * @param ord Ordinal value.
     * @return Enumerated value or {@code null} if ordinal out of range.
     */
    @Nullable
    public static CheckpointWriteOrder fromOrdinal(int ord) {
        return ord >= 0 && ord < VALS.length ? VALS[ord] : null;
    }
}