Michael Bayer wrote:
> On Nov 12, 2007, at 5:37 AM, Huy Do wrote:
>
>
>> Hi,
>>
>> I've just had a heck of a time getting transactions to behave
>> correctly
>> after upgrading to 0.4dev from 0.3.6, and I just wanted to make sure
>> that I am doing things correctly.
>>
>> I've found that to totally control transactions myself, and get ORM
>> sessions (i.e Session.flush()) to interact with SQL transactions i.e
>> table.insert().execute(), I had to do the following.
>>
>> engine = create_engine(appconfig.dburi, strategy='threadlocal',
>> echo=False)
>> Session = scoped_session(sessionmaker(bind=engine, autoflush=False,
>> transactional=False))
>> metadata = MetaData(engine)
>>
>> then.
>>
>> engine.begin()
>> try:
>> // Session.flush()
>> // mytable.insert().execute() stuff
>> engine.commit
>> except:
>> engine.rollback()
>>
>> Does this seem correct ?
>>
>> Previously i used autoflush=True, transactional=True together with
>> Session.begin(), Session.commit(), Session.rollback() and I ran into
>> all
>> sorts of issues e.g transaction was started but never committed etc.
>>
>>
>
> The reason you have to use "threadlocal" in that case is because you
> are relying upon "implicit" execution of things like mytable.insert(),
> and you also want the transaction to propigate from engine to session
> without explicitly passing the connection to it. so what youre doing
> above is OK. it might actually be the easiest way to do it and is
> the only way the "implicit" execution style can participate in the
> transaction.
>
Great. Thanks for the confirmation.
> 2. use the engine to manage the transaction but dont use threadlocal:
>
> conn = engine.connect()
> trans = conn.begin()
> Session(bind=conn)
> try:
> # ....
> conn.execute(mytable.insert(), stuff)
> trans.commit()
> except:
> trans.rollback()
> finally:
> Session.close()
>
There's no way i'm giving up threadlocal :-) I love it (at least in my
web programs).
I have this transaction decorator which I wrap all my data access code
in, and with SA's cool transaction support, I don't have to worry about
transaction commit/rollback handling again.
def transaction(func):
'''
This is a decorator for wrapping methods in a db transaction
'''
def trans_func(*args, **kws):
engine.begin()
try:
f = func(*args, **kws)
engine.commit()
return f
except:
engine.rollback()
raise
return trans_func
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