On 11/16/2012 9:00 PM, Michael Bayer wrote:
On Nov 16, 2012, at 11:40 AM, Clemens Herschel, III wrote:
In a pyramid application:
In models.py: DBSession=
scoped_session(sessionmaker(extensions=ZopeTransactionExtension()))
In view: dbsession = DBSession
def add(request):
#get implant1
dbsession.add(implant)
transaction.commit()
dbsession = DBsession
This works fine on first add. On second call to add, the first
implant object is updated rather than an object added as I would
expect from the sqlalchemy session docs . Using a new session after
the commit is suggested in the zope-sqlalchemy docs to achieve this.
The user in this application might do repeated adds into many tables
in one request .
So because I want to use more than one session per request, I should
not use Zope-SQLAlchemy extension but SQLAlchemy ScopedSession helper
class. Is that correct? Please excuse any misuse of terminology.
Thanks for pointing me in the right direction.
Using SQLAlchemy0.7.3
zope-sqlalchemy0.6.1
there's misunderstanding here - whether an INSERT or UPDATE is emitted
is based on the state of the object passed to session.add(), whether
transient (INSERT) or detached (will become persistent and UPDATE will
be emitted for changes). These states are documented here:
http://docs.sqlalchemy.org/en/latest/orm/session.html#quickie-intro-to-object-states
. A transient object is only created via the constructor, "implant
= Implant()", or if a detached "implant" object is made transient
again using the make_transient() helper function. Else your object
is "detached" or "persistent" and refers to an existing row and can
only invoke an UPDATE or DELETE statement.
The code here doesn't describe what "implant" is, or where it comes
from, or what exactly "doesn't work fine" means as I don't see a
second call to "add()" here and I don't have detail on the context in
which this code excerpt is called.
There's a vague suggestion here that perhaps you're doing some kind of
master/slave/replication type of thing "the user might do repeated
adds into many tables in one request", there's different ways to
approach that of which using multiple Session objects bound to each
engine is just one, though a single Session can be made to refer to
multiple engines simultaneously (see
http://techspot.zzzeek.org/2012/01/11/django-style-database-routers-in-sqlalchemy/
for one example).
make_transient() may be a worthy helper here or even just a simple
"copy()" method on your "implant" object to make new transient instances.
Thanks for your help. There was a misunderstanding and general confusion
on my part. make transient() IS a worthy helper and I fixed my zope
transactions error as well.
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