On Sep 23, 2009, at 6:36 PM, phrrn...@googlemail.com wrote: > > I have a hidden WriterSession which I am using behind the scenes to > manage a number of API entries that write data in bulk e.g. upsert > (MappedClass, iterator_that_returns_dicts). I want the session to only > look at its own binds and to ignore any that are in place on the > metadata collection. I wrote my own get_bind that does this > (horrible!) hack: > > if self._Session__binds: > b = self._Session__binds > if c_mapper: > if c_mapper.base_mapper in b: > return b[c_mapper.base_mapper] > elif c_mapper.mapped_table in b: > return b[c_mapper.mapped_table] > > if self.bind: > return self.bind > > I don't really understand how the double underscore stuff works in > Python. Mike, how would you feel about exposing the session bind > information with an interface that is more amenable to subclassing?
The binds collection on Session is set via the "binds" argument, or one at a time using bind_mapper() and bind_table(). get_bind() does not consult the metadata's "bind" unless none of session.bind or or "__binds" has been configured. So there shouldn't be any need to hack get_binds(). Also I would strongly advise against using metadata.bind for any application that uses more than one engine. Here's what the 0.5 docs at http://www.sqlalchemy.org/docs/05/metadata.html#binding-metadata-to-an-engine-or-connection have to say: Note that the feature of binding engines is completely optional. All of the operations which take advantage of “bound” MetaData also can be given an Engine or Connection explicitly with which to perform the operation. Here's what 0.6 has to say at http://www.sqlalchemy.org/docs/06/metadata.html#binding-metadata-to-an-engine-or-connection : Binding the MetaData to the Engine is a completely optional feature. The above operations can be achieved without the persistent bind using parameters: (examples) Should you use bind ? It’s probably best to start without it. If you find yourself constantly needing to specify the same Engine object throughout the entire application, consider binding as a convenience feature which is applicable to applications that don’t have multiple engines in use and don’t have the need to reference connections explicitly. It should also be noted that an application which is focused on using the SQLAlchemy ORM will not be dealing explicitly with Engine or Connection objects very much in any case, so it’s probably less confusing and more “future proof” to not use the bind attribute. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalchemy@googlegroups.com To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en -~----------~----~----~----~------~----~------~--~---
