Android Room throws error: Deletion methods must either return void or return int (the number of deleted rows)

Question

I'm using Android Room with RxJava

dependencies {
    implementation 'androidx.room:room-rxjava2:2.1.0-alpha02'
}

I need to get Completable from parameterized deletion methods, I thought this feature is added as of 2.1.0? ex.

  @Query("DELETE FROM message_table WHERE uid = :id")
  Completable delete(String id);

  @Query("DELETE FROM message_table")
  Completable deleteAll();

Still throws error: Deletion methods must either return void or return int (the number of deleted rows).

Answer 1

As the error message is trying to tell:

With @Query, you have to change the returned data-type from Completable to int or void.

The Completable would need to subscribe to another method, which runs the method of the Dao:

Completable
  .fromAction(aMethodWhichCallsDao)
  .subscribeOn(Schedulers.single())
  .subscribe();

Or use the @Delete annotation, as @Commonsware suggested (in case this works as advertised).