On May 4, 2010, at 7:42 PM, chris e wrote:
I'll look into the new code. It does look simpler. I tried using the
MapperExtension functionality, but, the last time I tried to use it,
it did not allow for orm level changes(new items added to the session,
or attribute changes) to be made, as the UOW has already been
calculated. My main use case is business logic where child objects end
up updating parent items, or adding items to parent relations. Once
the UOW is calculated I have found that changes to items and their
relations are not caught, which makes sense.
yeah what I dont understand is why the order of things persisted matters when
you're inside of before_flush().the only thing that the sorting inside
flush determines, which has a visible effect on the ultimate outcome, is the
order of INSERT for a series of rows in a table. this is derived from the
order in which things were add()ed to the session, and is available ahead of
time off the instance_state.The only time this behavior might be more
complex is if one or more of the rows of one table are dependent on other rows
in that table. everything else about the order of things occuring has to do
with insert into table B before table A and so forth, nothing you need to
know if you arent issuing INSERT statements yourself within before_flush().
I'd love to have something in the public session/UOW api that provides
the items to be flushed in the order in which they are being flushed,
even though this may be an expensive operation.
On May 4, 4:17 pm, Michael Bayer mike...@zzzcomputing.com wrote:
On May 4, 2010, at 5:23 PM, chris e wrote:
I'm trying to provide functionality in a session extension for an
class to provide a 'before_flush' method that allows the class to make
changes to the session, and add additional items. To do this I need to
get the list of instances to be flushed to the database, and the order
in which sqlalchemy would commit the changes to the database. I then
reverse the order of this list so that items that the instances are
processed in the reverse order of the database commits. I used to do
this using some of the internal task functionality of UOW(see below),
but that is no longer available in 0.6.0. Any suggestions?
getting the order is pretty controversial.what elements of the order
are significant to you and why isn't this something you are tracking
yourself ? wiring business logic onto the details of persistence doesn't
seem like a good idea. Or are your flush rules related to SQL -level
dependencies, in which case why not let the flush handle it, or at least use
a MapperExtension so that your hooks are invoked within the order of flush ?
anyway, the order is available in a similar way as before if you peek into
what UOWTransaction.execute() is calling, namely _generate_actions().It
would be necessary for you to call this separately yourself which is fairly
wasteful from a performance standpoint. it returns a structure that is
significantly simpler than the old one but you'll still have to poke around
unitofwork.py to get a feel for it, since this isn't any kind of documented
public API (you obviously figured out the previous one, this one is simpler).
--
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
athttp://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.
--
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.
