mirror of https://github.com/M66B/FairEmail.git
55 lines
2.0 KiB
Kotlin
55 lines
2.0 KiB
Kotlin
/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package androidx.room.migration
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import androidx.sqlite.db.SupportSQLiteDatabase
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/**
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* Base class for a database migration.
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*
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* Creates a new migration between [startVersion] and [endVersion].
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*
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* Each migration can move between 2 versions that are defined by [startVersion] and
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* [endVersion].
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*
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* A migration can handle more than 1 version (e.g. if you have a faster path to choose when
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* going version 3 to 5 without going to version 4). If Room opens a database at version
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* 3 and latest version is 5, Room will use the migration object that can migrate from
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* 3 to 5 instead of 3 to 4 and 4 to 5.
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*
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* If there are not enough migrations provided to move from the current version to the latest
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* version, Room will clear the database and recreate so even if you have no changes between 2
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* versions, you should still provide a Migration object to the builder.
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*/
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abstract class Migration(
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@JvmField
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val startVersion: Int,
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@JvmField
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val endVersion: Int
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) {
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/**
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* Should run the necessary migrations.
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*
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* The Migration class cannot access any generated Dao in this method.
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*
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* This method is already called inside a transaction and that transaction might actually be a
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* composite transaction of all necessary `Migration`s.
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*
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* @param db The database instance
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*/
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abstract fun migrate(db: SupportSQLiteDatabase)
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}
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