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Hi Joe,

I think one independent job is finished in one session. The job is
responsible to start  a session, query or modify database then end the
session. Like port creating job in neutron, it starts a session, queries
network, adds port, allocates ip address, then ends the session at the end.

BR
Zhiyuan

On 31 July 2015 at 09:05, joehuang <joehuang at huawei.com> wrote:

> Hi, Vega,
>
>
>
> Multiple DB access will be a use case for one session , especially for DB
> data insertion, multiple table will be involved. To embed the session in
> Context, it’s ok to start a session if the session is empty, but how to
> decide when to commit the data, end a session?
>
>
>
> Best Regards
>
> Chaoyi Huang ( Joe Huang )
>
>
>
> *From:* Vega Cai [mailto:luckyvega.g at gmail.com]
> *Sent:* Thursday, July 30, 2015 3:03 PM
> *To:* openstack-dev at lists.openstack.org
> *Subject:* [openstack-dev] [tricircle] DAL implementation
>
>
>
> Hi folks,
>
>
>
> In my current implementation, there are a core module and a models module.
> Core module handles all the database stuff, start a session, issue sql
> operation, then end a session. Models module invokes methods in core module
> to access database, as showed below:
>
>
>
> model.py
>
> def get_site(site_id):
>
>     core.get_resource(Site, site_id)
>
>
>
> core.py
>
> def get_resource(model, pk_value):
>
>     # code to access database
>
>
>
> To add context, I am going to implement like this:
>
>
>
> model.py
>
> def get_site(context, site_id):
>
>     policy_check(context)
>
>     core.get_resource(Site, site_id)
>
>
>
> core.py
>
> def get_resource(model, pk_value):
>
>     # code to access database
>
>
>
> So there is no need to embed session into context.
>
>
>
> One advantage of embedding session into context is that you can combine
> more than one method calls in one session, like:
>
>
>
> model.py
>
> def complex_operation(context):
>
>     policy_check(context)
>
>     with context.session.begin():
>
>         core.operation1(context)
>
>         core.operation2(context)
>
>
>
> But this approach moves session handling from core module to models module
> and core module just provides some utility methods.
>
>
>
> I'm not sure which one is better.
>
>
>
> BR
>
> Zhiyuan
>
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