python - Why SQLAlchemy Session.filter().update/delete raise read-only exception when using RoutingSession? -

the following config, slave read-only:

engines = {                                                                             'master': create_engine(                                                                settings.master_url, echo=settings.echo_sql, pool_recycle=3600),                'slave': create_engine(                                                                 settings.slave_url, echo=settings.echo_sql, pool_recycle=3600),             }                                                                                     class routingsession(session):                                                          def get_bind(self, mapper=none, clause=none):                                           #return engines['master']                                                           if self._flushing:                                                                      return engines['master']                                                        else:                                                                                   return engines['slave']                                                  dbsession = scoped_session(sessionmaker(class_=routingsession)) 

when :

s = dbsession() #synchronize_session=false makes execution faster s.query(model).filter(model.id == 1).delete(synchronize_session=false) s.commit() 

it raises exception couldn't delete because of "read-only".

how rewrite routingsession make above 'delete' use 'master' database

---edit1---

i've done more test. above 'delete' different following 'delete' routingsession return 'master':

model = s.query(model).filter(model.id == 1).first() s.delete(model) s.commit() 

a query.delete() not part of "flush", typically if you're using routing session recipe, want implement using_bind() , call upon before operation delete():

class routingsession(session):      def get_bind(self, mapper=none, clause=none ):         if self._name:             return engines[self._name]         else:             # other cases here      _name = none     def using_bind(self, name):         s = routingsession()         vars(s).update(vars(self))         s._name = name         return s 

then use:

session().using_bind("master").query(model1).delete()