Migration



Base class for a database migration.

Each migration can move between 2 versions that are defined by startVersion and endVersion.

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.

If there are not enough migrations provided to move from the current version to the latest version, Room will might clear the database and recreate if destructive migrations are enabled.

Summary

Public constructors

Migration(startVersion: Int, endVersion: Int)

Creates a new migration between startVersion and endVersion inclusive.

Cmn
android
N

Public functions

open Unit

Should run the necessary migrations.

Cmn
android
N
open Unit

Should run the necessary migrations.

android

Public properties

Int
Cmn
android
N
Int
Cmn
android
N

Public constructors

Migration

Migration(startVersion: Int, endVersion: Int)

Creates a new migration between startVersion and endVersion inclusive.

Public functions

migrate

open fun migrate(connection: SQLiteConnection): Unit

Should run the necessary migrations.

This function is already called inside a transaction and that transaction might actually be a composite transaction of all necessary Migrations.

Parameters
connection: SQLiteConnection

The database connection

migrate

open fun migrate(db: SupportSQLiteDatabase): Unit

Should run the necessary migrations.

The Migration class cannot access any generated Dao in this method.

This method is already called inside a transaction and that transaction might actually be a composite transaction of all necessary Migrations.

This function is only called when Room is configured without a driver. If a driver is set using androidx.room.RoomDatabase.Builder.setDriver, then only the version that receives a SQLiteConnection is called.

Parameters
db: SupportSQLiteDatabase

The database instance

Throws
kotlin.NotImplementedError

if migrate(SQLiteConnection) is not overridden.

Public properties

endVersion

val endVersionInt

startVersion

val startVersionInt