IssueTracker

Component used: Room
Version used: 1.0.0-beta2
Devices/Android versions reproduced on: Nexus 5 / Android 6.0.1

- Sample project to trigger the issue.
- A screenrecord or screenshots showing the issue (if UI related).

It would be nice to support concurrent database access via WAL and connection pooling, but it seems not possible in the current version.

Connection pool can be enabled by calling SQLiteDatabase.enableWriteAheadLogging() or passing ENABLE_WRITE_AHEAD_LOGGING flag to open database in framework API. However when I tried to enable WAL for Room databases in the following codes, it failed with "java.lang.IllegalStateException: Write Ahead Logging (WAL) mode cannot be enabled or disabled while there are transactions in progress."

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        mAppDB = Room.databaseBuilder(this, AppDatabase.class, "app-db")
                .addCallback(new RoomDatabase.Callback() {
                    public void onCreate(@NonNull SupportSQLiteDatabase db) {
                        super.onCreate(db);
                        db.enableWriteAheadLogging();
                    }

                    public void onOpen(@NonNull SupportSQLiteDatabase db) {
                        super.onOpen(db);
                        db.enableWriteAheadLogging();
                    }
                })
                .build();
------------------

I hacked into FrameworkSQLiteOpenHelper and called FrameworkSQLiteOpenHelper.setWriteAheadLoggingEnabled(true) to enable WAL just after creating the OpenHelper. WAL and connection pool can be successfully enabled this way, but further access to the database will cause "SQLiteException: no such table: room_table_modification_log".

This is because InvalidationTracker create a temporary table called room_table_modification_log to track modifications to tables and trigger observer events, which can only be accessed in the main DB connection.

Is there a way to deal with Observers without using temporary tables? If it's not possible, how can I disable observer notifies and InvalidationTracker?