UnderTheHood.java

private QueryObservable createQuery(Func1<Set<String>, Boolean> tableFilter, String sql, String... args) {
    if(this.transactions.get() != null) {
      throw new IllegalStateException("Cannot create observable query in transaction. Use query() for a query inside a transaction.");
    } else {
      BriteDatabase.DatabaseQuery query = new BriteDatabase.DatabaseQuery(tableFilter, sql, args);
      final Observable queryObservable = this.triggers
        .filter(tableFilter) // Only trigger on tables we care about.
        .map(query) // DatabaseQuery maps to itself to save an allocation.
        .onBackpressureLatest() // Guard against uncontrollable frequency of upstream emissions.
        .startWith(query)
        .observeOn(scheduler)
        .compose(queryTransformer) // Apply the user's query transformer.
        .onBackpressureLatest() // Guard against uncontrollable frequency of scheduler executions.
        .doOnSubscribe(this.ensureNotInTransaction);
      return new QueryObservable(new OnSubscribe() {
        public void call(Subscriber<? super Query> subscriber) {
          queryObservable.unsafeSubscribe(subscriber);
        }
      });
    }
  }