IssueTracker

Component used: androidx.room:room-runtime
Version used: 2.1.0-alpha03
Devices/Android versions reproduced on: All devices. minSdk = 21. Most devices are Samsung (~90%)

I am getting tons of crashes and I am not able to reproduce them. Please see to attached stacktrace. I am using a default migration (drop everything -> recreate everything):

    @Provides
    @PerApplicationScope
    fun provideDatabase(application: Application): VintedDatabase {
        val builder = Room.databaseBuilder(
                application,
                VintedDatabase::class.java,
                "vinted_database.db"
        )
                .fallbackToDestructiveMigration()
        if (Debug.isDebuggerConnected()) {
            builder.allowMainThreadQueries()
        }
        return builder.build()
    }

The application is crashing on random DAO calls in various places in the app. There is a similar issue: https://issuetracker.google.com/issues/71014717#comment3 . However, this explanation doesn't apply to me, because I am not using migration. Please see attached generated code. The crash happens on line: _db.execSQL("DROP TABLE IF EXISTS `tracking_events`");

This generated code looks very stable. Also, everything at FrameworkSQLiteOpenHelper is synchronized, and I don't get how is possible to close DB during migration. But one thing caught my eye there:

        FrameworkSQLiteDatabase getWrappedDb(SQLiteDatabase sqLiteDatabase) {
            FrameworkSQLiteDatabase dbRef = mDbRef[0];
            if (dbRef == null) {
                dbRef = new FrameworkSQLiteDatabase(sqLiteDatabase);
                mDbRef[0] = dbRef;
            }
            return mDbRef[0];
        }

Just hypothetically, what if someone gets a DB through `FrameworkSQLiteOpenHelper.getWritableDatabase()` and closes immediate, like:

FrameworkSQLiteOpenHelper.getWritableDatabase().close()

Then DB instance will be closed and opening a new writable database gives a new SQLiteDatabase instance. But getWrappedDb returns an old one because the ref was not cleared because DB was closed directly instead of FrameworkSQLiteOpenHelper. Maybe some safety is needed here, like:

if (dbRef != null && dbRef.mDelegate != sqLiteDatabase) {
  //try to close old instance anyway to avoid memory leak
  dbRef.close()
  dbRef = null
}

//rest code

Need to mention, DAO requests could be done on a few IO threads. Maybe Single thread environment would be better?