/* * Copyright 2021 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 android.app.appsearch; import android.annotation.NonNull; import android.annotation.WorkerThread; /** * A migrator class to translate {@link GenericDocument} from different version of {@link * AppSearchSchema} * *
Make non-backwards-compatible changes will delete all stored documents in old schema. You can * save your documents by setting {@link Migrator} via the {@link * SetSchemaRequest.Builder#setMigrator} for each type and target version you want to save. * *
{@link #onDowngrade} or {@link #onUpgrade} will be triggered if the version number of the * schema stored in AppSearch is different with the version in the request. * *
If any error or Exception occurred in the {@link #onDowngrade} or {@link #onUpgrade}, all the * setSchema request will be rejected unless the schema changes are backwards-compatible, and stored * documents won't have any observable changes. */ public abstract class Migrator { /** * Returns {@code true} if this migrator's source type needs to be migrated to update from * currentVersion to finalVersion. * *
Migration won't be triggered if currentVersion is equal to finalVersion even if {@link * #shouldMigrate} return true; */ public abstract boolean shouldMigrate(int currentVersion, int finalVersion); /** * Migrates {@link GenericDocument} to a newer version of {@link AppSearchSchema}. * *
This method will be invoked only if the {@link SetSchemaRequest} is setting a higher * version number than the current {@link AppSearchSchema} saved in AppSearch. * *
If this {@link Migrator} is provided to cover a compatible schema change via {@link * AppSearchSession#setSchema}, documents under the old version won't be removed unless you use * the same document ID. * *
This method will be invoked on the background worker thread provided via {@link * AppSearchSession#setSchema}. * * @param currentVersion The current version of the document's schema. * @param finalVersion The final version that documents need to be migrated to. * @param document The {@link GenericDocument} need to be translated to new version. * @return A {@link GenericDocument} in new version. */ @WorkerThread @NonNull public abstract GenericDocument onUpgrade( int currentVersion, int finalVersion, @NonNull GenericDocument document); /** * Migrates {@link GenericDocument} to an older version of {@link AppSearchSchema}. * *
This method will be invoked only if the {@link SetSchemaRequest} is setting a lower * version number than the current {@link AppSearchSchema} saved in AppSearch. * *
If this {@link Migrator} is provided to cover a compatible schema change via {@link * AppSearchSession#setSchema}, documents under the old version won't be removed unless you use * the same document ID. * *
This method will be invoked on the background worker thread. * * @param currentVersion The current version of the document's schema. * @param finalVersion The final version that documents need to be migrated to. * @param document The {@link GenericDocument} need to be translated to new version. * @return A {@link GenericDocument} in new version. */ @WorkerThread @NonNull public abstract GenericDocument onDowngrade( int currentVersion, int finalVersion, @NonNull GenericDocument document); }