On May 7, 2008, at 7:08 AM, Martijn Faassen wrote:

Hi there (especially Christian),

I think we can work with explicits saves. In many cases the user won't have to worry about it anyway as the container object will do it for them (besides making the relation), or this 'query container' we spoke of will do it for them (but just the 'save' bit).

One point is that the scoped session approach itself doesn't work very well for using multiple databases in the same app. We could consider passing the session along in the containers during object graph wakling (or traversal) so an app can easily traverse into multiple databases. I'm not sure whether we can make the ORM do this for us though; does it initialize the mapping with a session?

SQLAlchemy's Session does support multiple engine binds itself, which most easily can be associated with particular mapped classes (i.e. vertical partitioning), so that a single session (or a scoped_session) can read and write data to the appropriate tables transparently (although things like joins across multiple databases will raise errors). Theres a horizontally-partitioning version of Session as well which obviously has a lot more caveats.

Using multiple sessions, one per DB is a valid approach as well. I'm not sure if Grok has other things going on when mulitple DBs are in use but SA's multi-bind capability is something to be aware of.
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