On Aug 3, 2010, at 6:45 PM, razamatan wrote: > so our db setup is that we have both vertical and horizontal > partitioning going on. > > first, is it possible to defined a session as a scoped, sharded > session to achieve both? namely, define the shardedsession wrapped by > a scoped session and simply have the various shard lookup functions > (*chooser) do the mapping for the vertical partition as well as the > horizontal ones? can this be cleanly done by using bind_table on the > session for the vertically partitioned ones and only have the various > shard lookup functions concern themselves with the horizontally > partitioned tables? > > failing the above, it seems pretty straightforward and possible > (although contrived) to use 2 different sessions (one sharded for > horizontal and one normal one for vertical w/ the table binds) to > achieve the same effect. however, we do lose out on the transaction > level details spanning all our db sessions. > > thoughts and advice appreciated. i'm clearly a nub when it comes to > this stuff.
well unfortunately so are the rest of us, I haven't actually tried using the horizontal sharding for anything though I have been aware of people who do. The key takeaway from the horizontal shard module is that you can rewrite the get_bind() method of Session to do anything you want, and there's just enough hooks so that you can get it to call get_bind() for each individual row its going to work with. So for an intricate scheme of database switching, the horizontal shard module and/or writing your own get_bind() will definitely work though write yourself a bunch of tests. Over here I have a project where I have not quite a horizontal shard scenario, but there are two databases used simultaneously - but after trying out a custom get_bind() situation that more or less worked, I am using just two separate scoped_sessions, only because there's not too much interaction between them and i really didnt want to confuse all the other developers, as the second DB isn't really used for most of the application. Its something you need to feel out. > > -- > You received this message because you are subscribed to the Google Groups > "sqlalchemy" group. > To post to this group, send email to sqlalch...@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. > -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To post to this group, send email to sqlalch...@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.
