public abstract class 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 fields
final int
final int

Public constructors
Migration(int startVersion, int endVersion)

Creates a new migration between startVersion and endVersion inclusive.

Public methods
abstract void

Should run the necessary migrations.

Public fields

endVersion

Added in 3.0.0-alpha01
public final int endVersion

startVersion

Added in 3.0.0-alpha01
public final int startVersion

Public constructors

Migration

Added in 3.0.0-alpha01
public Migration(int startVersion, int endVersion)

Creates a new migration between startVersion and endVersion inclusive.

Public methods

migrate

Added in 3.0.0-alpha01
public abstract void migrate(@NonNull SQLiteConnection connection)

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
@NonNull SQLiteConnection connection

The database connection