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added in version 1.0.0
belongs to Maven artifact android.arch.persistence.room:runtime:1.0.0

Migration

public abstract class Migration
extends Object

java.lang.Object
   ↳ android.arch.persistence.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

Fields

public final int endVersion

public final int startVersion

Public constructors

Migration(int startVersion, int endVersion)

Creates a new migration between startVersion and endVersion.

Public methods

abstract void migrate(SupportSQLiteDatabase database)

Should run the necessary migrations.

Inherited methods

From class java.lang.Object

Fields

endVersion

added in version 1.0.0
int endVersion

startVersion

added in version 1.0.0
int startVersion

Public constructors

Migration

added in version 1.0.0
Migration (int startVersion, 
                int endVersion)

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

added in version 1.0.0
void migrate (SupportSQLiteDatabase database)

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

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