| /* |
| * Copyright (C) 2017 The Android Open Source Project |
| * |
| * 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. |
| */ |
| |
| package androidx.room.migration; |
| |
| import androidx.annotation.NonNull; |
| import androidx.sqlite.db.SupportSQLiteDatabase; |
| |
| /** |
| * Base class for a database migration. |
| * <p> |
| * Each migration can move between 2 versions that are defined by {@link #startVersion} and |
| * {@link #endVersion}. |
| * <p> |
| * A migration can handle more than 1 version (e.g. if you have a faster path to choose when |
| * going version 3 to 5 without going to version 4). If Room opens a database at version |
| * 3 and latest version is >= 5, Room will use the migration object that can migrate from |
| * 3 to 5 instead of 3 to 4 and 4 to 5. |
| * <p> |
| * If there are not enough migrations provided to move from the current version to the latest |
| * version, Room will clear the database and recreate so even if you have no changes between 2 |
| * versions, you should still provide a Migration object to the builder. |
| */ |
| public abstract class Migration { |
| public final int startVersion; |
| public final int endVersion; |
| |
| /** |
| * Creates a new migration between {@code startVersion} and {@code endVersion}. |
| * |
| * @param startVersion The start version of the database. |
| * @param endVersion The end version of the database after this migration is applied. |
| */ |
| public Migration(int startVersion, int endVersion) { |
| this.startVersion = startVersion; |
| this.endVersion = endVersion; |
| } |
| |
| /** |
| * Should run the necessary migrations. |
| * <p> |
| * This class cannot access any generated Dao in this method. |
| * <p> |
| * This method is already called inside a transaction and that transaction might actually be a |
| * composite transaction of all necessary {@code Migration}s. |
| * |
| * @param database The database instance |
| */ |
| public abstract void migrate(@NonNull SupportSQLiteDatabase database); |
| } |