Hi Simon,
On 26/02/2014 13:18, Simon King wrote:
I don't know exactly what your needs are, but here's the example from the docs:
engine1 = create_engine('postgresql://db1')
engine2 = create_engine('postgresql://db2')
Session = sessionmaker(twophase=True)
# bind User operations to engine 1, Account operations to engine 2
Session.configure(binds={User:engine1, Account:engine2})
Interesting, didn't know you could do that. However, how does that scale
to lots of mapped classes? I guess User and Account would need to have
different declarative bases? Is there a way to say all classes for a
particular base go to a particular engine?
# commit. session will issue a flush to all DBs, and a prepare
step to all DBs,
# before committing both transactions
session.commit()
...and I guess, if configured, this would wire in two phase commits
correctly?
Partially innocent question: If one of the flushes you describe above
fails (say with an integrity error), then the transactions would be left
in need of a rollback on all engines and definitely no data would be
committed?
cheers,
Chris
So in this case there are 2 engines, pointing at 2 different DBs.
Operations against the "User" class will use engine1, and operations
against the Account class will use engine2. session.commit() will use
two-phase operations to ensure that both get committed together.
I think the magic happens within the Session.get_bind() method:
http://docs.sqlalchemy.org/en/rel_0_9/orm/session.html#sqlalchemy.orm.session.Session.get_bind
http://docs.sqlalchemy.org/en/rel_0_9/orm/session.html#sqlalchemy.orm.session.Session.params.binds
Would that work in your situation?
Simon
On Wed, Feb 26, 2014 at 12:50 PM, Chris Withers <[email protected]> wrote:
Hi Simon,
The problem is that I want to use multiple sessions, I think.
How would I have connections to multiple databases with differing schemas
using a single Session?
cheers,
Chris
On 25/02/2014 18:14, Simon King wrote:
I've never used two-phase commit, but can you get away with just a
single session, like the example at:
http://docs.sqlalchemy.org/en/rel_0_9/orm/session.html#enabling-two-phase-commit
Simon
On Tue, Feb 25, 2014 at 6:07 PM, Chris Withers <[email protected]>
wrote:
No takers? :'(
On 19/02/2014 18:43, Chris Withers wrote:
Hi All,
My other usual question now ;-)
I have multiple databases that I'm connecting to from my application. I
need to commit or rollback a single transaction across all of them.
So, two phase commit, right?
Okay, but how do I tie the sessions together? What and how do I call
commit?
Is there anything better than zope.transaction? (which does address this
need...)
Chris
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