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Class doesn't exist in current schema after being added to migration

I've been struggling performing a simple migration. What I just want to achieve is add a new Class in realm.
The code below is inside a method that is called inside onCreate.
Realm.init(this)
val config = RealmConfiguration.Builder()
.name("db_name")
.schemaVersion(5L)
.migration { realm, oldVersion, newVersion ->
val schema = realm.schema
var _oldVersion = oldVersion
if (_oldVersion == 4L) {
if (schema.contains(XModel::class.java.simpleName))
schema.remove(XModel::class.java.simpleName)
if (!schema.contains(XModel::class.java.simpleName))
schema.create(XModel::class.java.simpleName)
.addField(XModel::id.name, Long::class.javaPrimitiveType,
FieldAttribute.PRIMARY_KEY)
...
.addField(XModel::N.name, Int::class.javaPrimitiveType)
_oldVersion += 1
}
}
.build()
Realm.setDefaultConfiguration(config)
As what the title suggest, the new class in the schema was created inside the migration object, but when I try to access it in other parts of the application using a realm query or a simple call to schema.get("XModel") it will throw an error XModel doesn't exist in current schema. Any comment will really help. Thank you...
Edit:
Additional information. I have 2 realm objects, each are in different android modules, one module is dependent to the other. I somehow have some progress, now Im a bit confuse, do I need to declare 2 configurations? Then it would mean 2 realm instance? How to switch from both, I want to merge them into 1 realm.
Edit2:
Another clarification about realm. If you have 2 android modules, each of them using realm, will they have different realm even if in the realm configuration they have the same name?
Background
I want to give you a background of what im doing because I think its needed to fully understand my case.
Originally I only have one module, but then after refactoring and also because of future apps to be develop, I need to pull out the common classes from the existing module and put it in a separate lower-level module that the future apps can depend on. This new lower-level module will also be responsible for most of the data layer, so realm was transferred to this module. But I can't just ignore the realm of the existing app because some users might already populated it, and I need to transfer those data to the new database.

Room cannot verify the data integrity in Android

MainActivity class
public class MainActivity extends BaseActivity {
private AppDatabase db;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// Database creation
db = Room.databaseBuilder(getApplicationContext(),
AppDatabase.class, "Medimap-db").build();
// Profile profile=new Profile("rajitha","12-2-345","male","no 345","test med","test emergency","testurl");
// db.profileDao().insert(profile);
// Toast.makeText(getApplicationContext(),"success",Toast.LENGTH_SHORT).show();
new DatabaseAsync().execute();
}
private class DatabaseAsync extends AsyncTask<Void, Void, Void> {
#Override
protected void onPreExecute() {
super.onPreExecute();
//Perform pre-adding operation here.
}
#Override
protected Void doInBackground(Void... voids) {
//Let's add some dummy data to the database.
Profile profile = new Profile("rajitha", "12-2-345", "male", "no 345", "test med", "test emergency", "testurl");
db.profileDao().insert(profile);
return null;
}
#Override
protected void onPostExecute(Void aVoid) {
super.onPostExecute(aVoid);
Toast.makeText(getApplicationContext(), "success", Toast.LENGTH_SHORT).show();
//To after addition operation here.
}
}
}
AppDatabase class
#Database(entities = {Profile.class, Medicine.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {
public abstract ProfileDao profileDao();
public abstract MedicineDao medicineDaoDao();
}
ProfileDao
#Dao
public interface ProfileDao {
#Query("SELECT * FROM profile")
List<Profile> getAll();
// #Query("SELECT * FROM user WHERE uid IN (:userIds)")
// List<Profile> loadAllByIds(int[] userIds);
// #Query("SELECT * FROM user WHERE first_name LIKE :first AND "
// + "last_name LIKE :last LIMIT 1")
// User findByName(String first, String last);
#Insert
void insertAll(Profile... profiles);
#Insert
void insert(Profile profile);
#Delete
void delete(Profile profile);
}
Here I got an error after the first run of the app. It seems like the app is trying to create DATABASE once again, but there already is an existing one so they suggested to change the version code. My requirement is that I only need to insert a new data set. How can I achieve that? Thanks in advance. Here is the logcat error:
Caused by: java.lang.IllegalStateException: Room cannot verify the data integrity. Looks like you've changed schema but forgot to update the version number. You can simply fix this by increasing the version number.

Android 6.0+
For those of you who come across this now a days, simply uninstalling might not help and it will drive you nuts, so before you have to figure it out, let me share the issue: Google introduced the "autobackup" functionality in
Android 6.0, which brings back a DB when you reinstall. (https://developer.android.com/guide/topics/data/autobackup.html)
You can simply add...
<application ...
android:allowBackup="false">
</app>
...to disable this functionality and you are good to go (now you can simply uninstall to delete the database).

If you're only developing the application at the moment, it means that you are not on Production and uninstalling the app from device and install it again will work as required.

Increase the version:
#Database(entities = {EmployeeEntry.class}, version = 2, exportSchema = false)
Took from
link

If you don't care about migrations when update entities:
Increase database version
Add fallbackToDestructiveMigration() method at the time of building database, e.g:
Room.databaseBuilder(appContext, AppDatabase.class, "appdb.db")
.fallbackToDestructiveMigration()
.build();
Hope this help someone ;)

There are 3 ways to fix this data integrity exception.
1) If you don't want to increase your Database version and you can bear data loss
Just clear your App data from App settings after installing new build in device and launch App again, it would work without data integrity exception
2) If you can increase your Database version but still you can bear data loss
If you want to make it seamless( no crash due to schema update), you can simply increase Database version (let say from 1 to 2) and mention Default migration strategy in Database Builder fallbackToDestructiveMigration(). Then on installing this App, your previous DB data would clear up and you wouldn't get this data integrity exception.
3) If you can increase your Database version and also want to save your previous data
You need to increase your Database version(let say from 1 to 2) but also need to implement proper migrations logic (based on your lower version and higher version) in your App. Then on installing new version, you will not get this data integrity exception.
For migrations of Room you can read out this nice article written for migrations
For official documentation of Room migrations go to link

In my case, reinstalling didn't help and also I couldn't set android:allowBackup:true because one of the libraries I had used required it. So I went to Settings > Apps > My app, and cleared data and memory for that app. Problem gone;)

Step 1: Install new build
Step 2: Clear all app data from Settings.
Step 3: Open app ( will work fine now )

You can also use adb shell pm uninstall com.package.app in your terminal to fully uninstall the app. After that, install it again and the error will disappear.

How to compare Realm schemas from Android and iOS realm file

I've implemented database in realm on Android an iOS. I'm hardly sure that they are the same but if I'm replacing file from iOS and getting Realm instance using this file I get RealmMigrationNeededException. Is there any way to compare schemas in realm files from Android and iOS? If I'm doing the same action with file from another Android device it works.
Edit:
After adding empty Migration:
public class Migration implements RealmMigration {
#Override
public long execute(Realm realm, long version) {
return version;
}
}
I get: "Primary key not defined for field 'id' in existing Realm file. Add #PrimaryKey." Both platforms have 'id' field implemented as primary key.

There doesn't exit a tool yet that can output the entire schema unfortunately. You can use our Realm Browser for IOS, which will show you some of it, but if I remember correctly it will not show you e.g which fields are indexed: https://itunes.apple.com/us/app/realm-browser/id1007457278?mt=12
The migration exception should give you some idea what is wrong though?

RealmMigrationNeededException when changing Realm model [duplicate]

This question already has answers here:
"realm migration needed", exception in android while retrieving values from realm db
(5 answers)
Closed 5 years ago.
Whenever I change the model like adding more fields, the app crash with io.realm.exceptions.RealmMigrationNeededException error. This can only be resolved when I uninstalled and reinstalled the app.
Any suggestion to do migration? I am using only the default instance.

If you don't have any problem in loosing your old data then you can delete Realm Configuration and create new one.
Realm realm = null;
try {
realm = Realm.getInstance(MainActivity.this);
} catch (RealmMigrationNeededException r) {
Realm.deleteRealmFile(MainActivity.this);
realm = Realm.getInstance(MainActivity.this);
}
OR
RealmConfiguration config2 = new RealmConfiguration.Builder(this)
.name("default2")
.schemaVersion(3)
.deleteRealmIfMigrationNeeded()
.build();
realm = Realm.getInstance(config2);
you have to do Migration if you don't want to loose your data please see this example here.

You should be able to find the information you need here:
https://realm.io/docs/java/latest/#migrations
Just changing your code to the new definition will work fine, if you
have no data stored on disk under the old database schema. But if you
do, there will be a mismatch between what Realm sees defined in code &
the data Realm sees on disk, so an exception will be thrown.

Realm migrations in 0.84.2 are changed quite a bit, the key points on making a realm (0.84.2) migration work for me were understanding that:
The schemaVersion is always 0 when your app has a realm db without
specifying the schemaVersion. Which is true in most cases since you
probably start using the schemaVersion in the configuration once you
need migrations & are already running a live release of your app.
The schemaVersion is automatically stored and when a fresh install of your app occurs and you are already on schemaVersion 3, realm
automatically checks if there are exceptions, if not it sets the
schemaVersion to 3 so your migrations aren't run when not needed.
This also meens you don't have to store anything anymore in
SharedPreferences.
In the migration you have to set all values of new columns when the type is not nullable, ...
Empty Strings can be inserted but only when setting convertColumnToNullable on the column

How to test database migration in Android?

I have an Android app with a database with version 1.
Now I like to change the structure of the database and write all the migration code etc.
The problem I have is how to test this.
I need to repeatedly have the old version of the app with its old DB so I can test the update process to the new app with the new DB several times.
I thought to simplify things I make a copy of my project and just rename it new - leaving the manifest and everything unchanged!!!!
The idea is to run/install the old version of the app with the old DB structure using Eclipse so I can create the start situation of my update.
Now to simulate the user update to the new app version I install it just over the old version using Eclipse again) - but even without having changed the db I get an error that the DB already exists ???
I am confused (I have only changed the project name, not the manifest) I would have expected that I can just install the new version over the old version and hereby test the user update of the app.
But that does not work.
How would I best do this? (without having the old and the new database code in the very same project. since if I have the same project I have two different data base structures in there and need to build in a switch how it should start up, ie as old or new. I find it cleaner to just write the new version of the app with the new database structure in there)

Room is one of the Android Architecture Components for database stuff.
Room provides a testing Maven artifact to assist with this testing process.
First you need to export db scheme by set the room.schemaLocation annotation processor property in your build.gradle file
android {
...
defaultConfig {
...
javaCompileOptions {
annotationProcessorOptions {
arguments = ["room.schemaLocation":
"$projectDir/schemas".toString()]
}
}
}
}
#RunWith(AndroidJUnit4.class)
public class MigrationTest {
private static final String TEST_DB = "migration-test";
#Rule
public MigrationTestHelper helper;
public MigrationTest() {
helper = new MigrationTestHelper(InstrumentationRegistry.getInstrumentation(),
MigrationDb.class.getCanonicalName(),
new FrameworkSQLiteOpenHelperFactory());
}
#Test
public void migrate1To2() throws IOException {
SupportSQLiteDatabase db = helper.createDatabase(TEST_DB, 1);
// db has schema version 1. insert some data using SQL queries.
// You cannot use DAO classes because they expect the latest schema.
db.execSQL(...);
// Prepare for the next version.
db.close();
// Re-open the database with version 2 and provide
// MIGRATION_1_2 as the migration process.
db = helper.runMigrationsAndValidate(TEST_DB, 2, true, MIGRATION_1_2);
// MigrationTestHelper automatically verifies the schema changes,
// but you need to validate that the data was migrated properly.
}
}
You can read an official document for more info

You can create the main file 'create.sql' and the migrations files called '1.sql, 2.sql,.., n.sql'.
Store all these files in assets for example.
If the user has no database, apply create.sql
If the user needs a database upgrade from A to Z, then apply a+1.sql, a+2.sql, …, z.sql.
You need implement applyUpgrades method that you'll use on upgrade version of DB and for migration tests. It's look like:
fun Context.applyUpgrades(db: SQLiteDatabase, from: Int, to: Int): Unit =
(from+1..to).forEach { index ->
val migrationSql = getMigrationFromAssets(index)
db.execSQL(migrationSql)
}
Your migration tests will look like:
#Test
fun upgrade10to11() { // when you upgrade from 10 to 11
val db = SQLiteDatabase.create(null)
// apply all previous migrations
applyUpgrades(db, from = INITIAL, to = 10)
val valuesBefore = ..
// our new migration
applyUpgrades(db, from = 10, to = 11)
val valuesAfter = ..
// assert that valuesBefore and valuesAfter are correct
}
Also you can check that you did not forget write test for new migration:
#Test
public void hasAllNecessaryTests() {
assertEquals(DB_VERSION, 11);
}
Trello bless

As you only need the data and structures to test migration, you could make backups of the old databases and use them in your tests.
So for each test:
install app, put data in, make backup (once)
restore backup, run test (often)
That way you only have to make the backup once and can restore them on every test.
If your tests are automated, you could even restore the backups automatically as well.
For SQLite, making backups is as easy as copying the database file, but pretty much every database has a way to make and restore backups.
Your updated app seems to try to create the database (not the data inside) again, but with the database of the old app still being around that won't work.
This may be caused by the app not noticing it was installed before.