Register now for Android Dev Summit 2019!

Migration

abstract class Migration
kotlin.Any
   ↳ androidx.room.migration.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 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.

Summary

Public constructors

<init>(startVersion: Int, endVersion: Int)

Creates a new migration between startVersion and endVersion.

Public methods

abstract Unit
migrate(@NonNull database: SupportSQLiteDatabase)

Should run the necessary migrations.

Properties

Int

Int

Public constructors

<init>

Migration(startVersion: Int, endVersion: Int)

Creates a new migration between startVersion and endVersion.

Parameters
startVersion Int: The start version of the database.
endVersion Int: The end version of the database after this migration is applied.

Public methods

migrate

abstract fun migrate(@NonNull database: SupportSQLiteDatabase): Unit

Should run the necessary migrations.

This 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.

Parameters
database SupportSQLiteDatabase: The database instance

Properties

endVersion

val endVersion: Int

startVersion

val startVersion: Int