On Apr 7, 2009, at 6:07 PM, rintin...@googlemail.com wrote:
>
> Hey Everyone,
>
> I'm new to SQLAlchemy (used to using Django's ORM but need to switch)
> and there's just one thing I'm struggling with, which is when am I
> supposed to create Sessions? I am of course creating "scoped
> sessions". I feel like a real dunce for not being able to get my head
> around it.
>
> Do I create one per-request and pass it around? That just doesn't feel
> quite right to me. Or can I create them at module-level when I need
> them?
per-request is the most natural approach. The point of the
"scopedsession" is that you can use it as a "global" object, there's
no need to pass it around. It automatically routes operations to a
thread-local session. I'm sure django does something similar. the
chapter on sessions includes a discussion on integrating scopedsession
within a web application, you should check it out.
> Also, is it okay to call commit() more than once on the same
> session?
absolutely.
> On a per-function basis even (seems like an awful lot of
> boilerplate code in each function though… surely not?!)
depending on what you're doing , this may or may not be appropriate.
boilerplate can be cut down using a decorator, such as:
@commits
def do_some_stuff(...):
....
the decorator:
def commits(fn):
def go(*args, **kw):
try:
return fn(*args, **kw)
Session.commit()
except:
Session.rollback()
raise
return go
Session is a scopedsession which can be declared at the module level.
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