Can Android-Room auto-create migrations?

Question

When working with Room for sqlite libraries on Android, I notices that while the tables for the first version of the DB are created automatically, I saw only tutorials on how to migrate to a newer version by manually writing the sql-commands for the Migration-classes.

This seems really odd as it is possible to auto-generate these migrations (e.g. like django) and it's suprising that the create-commands for V1 are autogenerated, but if I add a table later, I have to manually type the commands.

So did I just miss it or do I really have to write the migrations?

[This](https://stackoverflow.com/questions/48399852/room-database-migration-if-only-new-table-is-added/54045368#54045368) might help — musooff, Aug 12 '19 at 02:57

score 6 · Answer 1 · answered Oct 30 '21 at 09:43

It is supported now from room 2.4.0.

For now beta version only available 2.4.0-beta01. I have tested in my project its working fine.

// Database class before the version update.
@Database(
  version = 1,
  entities = {User.class}
)
public abstract class AppDatabase extends RoomDatabase {
  ...
}

// Database class after the version update.
@Database(
  version = 2,
  entities = {User.class},
  autoMigrations = {
    @AutoMigration (from = 1, to = 2)
  }
)
public abstract class AppDatabase extends RoomDatabase {
  ...
}

See doc

The Syntax is totally changed.. Anyone who is looking for answer - Check Doc — Vetalll, Sep 20 '22 at 19:46

score 2 · Answer 2 · answered Aug 12 '19 at 01:51

In my experience, you have to manually create the migrations for Google Room. Maybe one of the reasons why you are going to migrate is to preserve/handle the data saved safely on your SQLite database.

For instance that you do destructive migration:

Room.databaseBuilder(context.getApplicationContext(),
                    UsersDatabase.class, "Sample.db")
            .fallbackToDestructiveMigration()
            .build();

This will try to delete your database, will recreate your schema and also your data will be gone.

So for migration, like

Room.databaseBuilder(context.getApplicationContext(),
    UsersDatabase.class, "Sample.db")
    .addMigrations(MIGRATION_1_2)
    .build();

You are manually managing your database migration and you'll be responsible for all the data. For example, you added a new property/column to User table, you'll have to create a migration for that saying alter the user table and add the new property with a default value of blah blah blah...

I also give some advise, if you'll do migrations, do it carefully, or else it will give you a headache, and your app will produce migration-related crashes.

score 1 · Answer 3 · answered Aug 11 '19 at 20:03

1

No it can not, You have to write Room migrations.

Check this tutorial to write migrations.

I noticed Room does not have a good Migration System

answered Aug 11 '19 at 20:03

Mahmoud Waked

357
2
8

score 1 · Answer 4 · answered Jun 06 '21 at 08:41

1

Automigration is supported from version 2.4.0

https://developer.android.com/reference/androidx/room/AutoMigration

answered Jun 06 '21 at 08:41

Mr.G

1,275
1
18
48

score 0 · Answer 5 · answered Aug 11 '19 at 20:02

0

Presently, with Room, you really have to write the migrations.

answered Aug 11 '19 at 20:02

CommonsWare

986,068
189
2,389
2,491

Do you have an idea why this (imho important) feature was not implemented? – FooTheBar Aug 11 '19 at 20:03
@FooTheBar: If I had to guess, they have not gotten around to it yet. – CommonsWare Aug 11 '19 at 20:05

Can Android-Room auto-create migrations?

5 Answers5