Return value from DB operation in Single<Long>

I am adding a record in my database (Room) and it returns the ID of the inserted record. For example, I add a row and it returns the number 5 (which is a Long).

When that operation is complete, I need to pass that ID to another function. When this 2nd function is complete, I need to return the ID which I got from step 1.

I am using RxJava and I am subscribing to the response, as I need to perform another action when this is complete, using the DB record ID.

See below:

@Insert(onConflict = OnConflictStrategy.REPLACE)
fun saveUserData(date: UserDataDatabaseModel): Long

This returns the Long of the row ID.

I call it like this:

override fun submitUserData(): Single<Long> {
    var rowId: Long = -1
    return Completable.fromAction {
        rowId = dao.saveUserData(getUserData())
    }.andThen { 
        uploadUserData(rowId)
    }.andThen(Single.just(rowId))
}

At the call point, I do this:

submitUserData()
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread())
        .doOnError { throwable -> throwable.printStackTrace() }
        .subscribe({ rowId ->
            //handle rowId
        },{
            //handle error
        })

The issue I have is that the code never returns to the subscribe.
If I debug and use LogCat etc, then the last place I see the code being called is in the .andThen(uploadUserData()) code.

So I think I need to replace the Completable part of the code and replace it with something like Single.create(). I did try this already and got a similar problem where the code stopped executing after the first block, like it wasn't being subscribed to.

Can anyone help me with this?
Thanks

First of all you don't need additional variable outside the reactive flow, and now

1. why don't you just call

   Single.fromCallable{
   dao.saveUserData(getUserData()).apply {
   uploadUserData(it) //non rx call
   }
   }

2. if you really need to split calls to different Observables

   Single.fromCallable{ dao.saveUserData(getUserData()) }
   .flatMap { rowId -> uploadUserData(rowId).map {_ -> rowId }}