Android Room requery on db change

Question

I'm writing an application using newest Room Persistance Library. The app sipmply shows a list of items and updates this list as data changes.

When new item is inserted into a table, or updated, I expect the list to update automaticlally.

I tried vanilla LiveData and Flowable so far. Both are claimed to support this feature, as it is stated in documentation and on this blog: https://medium.com/google-developers/room-rxjava-acb0cd4f3757

Here's the ViewModel snippet in Kotlin:

messagesFlowable = db.messagesDao().all()
messagesFlowable
        .observeOn(AndroidSchedulers.mainThread())
        .subscribe {
            Log.d(TAG, "Received 1 list of %s items", it.size)
            messages.value = it
         }

Somewhere else, the db is modified like this:

mDb.messagesDao().add(Message("Some data"))

The updates are not pushed to observers. I guess I'm missing something, but what?

Update: This problem is solved and the answer is below.

Answer 1

I'll answer my own question, as the solution is not documented.

It looks like you need to have the same instance of database object. In my case, my Dagger2 was misconfigured to inject new instances of DB each time, so my Repository and ViewModel ended up with 2 separate instances.

Once I use single database instance shared among all interested parties, all updates are distributed correctly.