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()} 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 # 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 <javascript:>> 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/ > > > > To post example code, please provide an MCVE: Minimal, Complete, and > Verifiable Example. See http://stackoverflow.com/help/mcve for a full > description. > > --- > > You received this message because you are subscribed to the Google > Groups "sqlalchemy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to sqlalchemy+...@googlegroups.com <javascript:>. > > To post to this group, send email to sqlal...@googlegroups.com > <javascript:>. > > Visit this group at https://groups.google.com/group/sqlalchemy. > > For more options, visit https://groups.google.com/d/optout. > -- SQLAlchemy - The Python SQL Toolkit and Object Relational Mapper http://www.sqlalchemy.org/ To post example code, please provide an MCVE: Minimal, Complete, and Verifiable Example. See http://stackoverflow.com/help/mcve for a full description. --- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at https://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/d/optout.