Oh, it's perfect for me if I can use bases for bindings.
Thank you
Le mardi 6 novembre 2018 21:27:19 UTC+2, Mike Bayer a écrit :
>
> On Tue, Nov 6, 2018 at 2:20 PM <yoch....@gmail.com <javascript:>> wrote:
> >
> > I have many classes, so it's seems a better idea to use something like
> that (but I don't know what exactly is this registry, and why it's a
> WeakRef dict) :
> >
> > binding = {cls: engine for cls in Base._decl_class_registry.values()}
>
>
> see I don't want you to use that because it's a private variable. You
> should make your own "registry" as you do the automap.
>
>
> >
> > If not, maybe I can use the second approach, overloading Session, but is
> this safe ?
> >
> > class BindSession(Session):
> > def get_bind(self, mapper=None, clause=None):
> > if mapper:
> > if issubclass(mapper.class_, SomeBase):
> > return some_engine
> > elif issubclass(mapper.class_, OtherBase):
> > return other_engine
>
> oh is it based on two different bases? Guess what, you can use those
> base classes:
>
> session = Session(binds={SomeBase: engine1, OtherBase: engine2})
>
> docs seem to not be in-depth enough or adequately cross-linked, will fix
>
>
>
> > # correct ?
> > return super().get_bind(mapper,clause)
> >
> >
> >
> >
> >
> >
> >
> >
> > Le mardi 6 novembre 2018 18:07:48 UTC+2, Mike Bayer a écrit :
> >>
> >> On Tue, Nov 6, 2018 at 9:41 AM <yoch....@gmail.com> wrote:
> >> >
> >> > Hi,
> >> >
> >> > I'm using a schema with multiple DB, like :
> >> >
> >> > engine1 =
> create_engine("mysql://localhost/{db}?charset=utf8".format(db=db1))
> >> > engine2 =
> create_engine("mysql://localhost/{db}?charset=utf8".format(db=db2))
> >> >
> >> > Then I use automap and reflection to generate mapping of all classes
> needed.
> >> >
> >> > Sometime, I want to use classes from both databases, but I cannot
> bind my session directly with two engines.
> >> >
> >> > I noticed that I can use the Session `binds` argument to decide which
> class to bind to some engine, but I have many classes to include here, and
> this is somewhat error prone.
> >> >
> >> > Is there any solution to automate the binding definition against each
> class ? Or to bind a session directly to multiple engines ?
> >>
> >> you would use the "binds" argument as you saw in
> >>
> https://docs.sqlalchemy.org/en/latest/orm/session_api.html#sqlalchemy.orm.session.Session.params.binds.
>
>
> >>
> >> as you noticed though, you have to tell the Session which classes map
> >> to which engine. So when you use automap, each time you reflect()
> >> for a particular engine, you need to gather all the classes that were
> >> generated for that call and add them to a dictionary, which you can
> >> then pass to session.binds.
> >>
> >> If you have some totally other way to tell the Session, given a class,
> >> which engine to use, you can also make your own method to do whatever
> >> you want and override it, by overriding get_bind:
> >>
> https://docs.sqlalchemy.org/en/latest/orm/session_api.html#sqlalchemy.orm.session.Session.get_bind
>
> >> . you probably don't need to do it this way but there's an example
> >> of how that looks at
> >>
> http://techspot.zzzeek.org/2012/01/11/django-style-database-routers-in-sqlalchemy/.
>
>
> >>
> >>
> >>
> >> >
> >> > Thank you
> >> >
> >> >
> >> > --
> >> > SQLAlchemy -
> >> > The Python SQL Toolkit and Object Relational Mapper
> >> >
> >> > http://www.sqlalchemy.org/
> >> >
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> > --
> > SQLAlchemy -
> > The Python SQL Toolkit and Object Relational Mapper
> >
> > http://www.sqlalchemy.org/
> >
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--
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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