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Janzert  
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 More options Apr 16 2007, 4:47 pm
From: Janzert <janz...@gmail.com>
Date: Mon, 16 Apr 2007 16:47:16 -0400
Local: Mon, Apr 16 2007 4:47 pm
Subject: Re: Help with implicit transactions

Alberto Valverde wrote:

> On Apr 16, 2007, at 6:53 PM, George Sakkis wrote:

>> On Apr 16, 12:18 pm, Alberto Valverde <albe...@toscat.net> wrote:
>>> On Apr 16, 2007, at 5:54 PM, George Sakkis wrote:

>>>> Is there any way I can force a COMMIT within an exposed method ?  
>>>> I am
>>>> using SqlAlchemy with PostgreSQL and I am creating a few records  
>>>> that
>>>> I need to use for subsequent SELECTs within the same method.  
>>>> Although
>>>> I do flush() them and get their assigned IDs, subsequent explicit
>>>> SELECTs (using SA's select(), not the data mappers) fail to see the
>>>> changes.
>>> How are you obtaining the engine when you use SA's select? You should
>>> use the same connection the transaction is using so you see its
>>> changes, check out [1]
>> I use:

>> from turbogears import database as db
>> engine=db.get_engine()

>> How can I access the implicit transaction created by TG or its
>> connection object ?

> You'll need access to the transaction instance. Unfortunately it's a  
> local variable inside database.sa_rwt. Perhaps it should be bound to  
> cherrypy.request so you could do:

> connection = engine.connect()
> cherrypy.request.sa_transaction.add(connection)

> then connection.execute(table.select()) # or whatever

> as described in the mentioned link. Can you try this patch see if it  
> works?

> Index: turbogears/database.py
> ===================================================================
> --- turbogears/database.py      (revision 2824)
> +++ turbogears/database.py      (working copy)
> @@ -336,7 +336,8 @@
> [run_with_transaction.when("_use_sa()")]
> def sa_rwt(func, *args, **kw):
>       log.debug("New SA transaction")
> -    transaction = session.create_transaction()
> +    req = cherrypy.request
> +    transaction = req.sa_transaction = session.create_transaction()
>       try:
>           retval = func(*args, **kw)
>           transaction.commit()

> Alberto

It would be nice if instead of holding onto a local reference to the
transaction it used the one in the request object to commit and rollback
(i.e. get rid of the transaction variable above and change all
references to req.sa_transaction). I believe this would solve the
problem where people want to be able to rollback the transaction and
then start a new one within a controller.

Janzert


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