Israel,
On Mar 17, 2011, at 4:48 PM, Xavier (DBIYF) wrote:
> On 18/03/11 10:26 AM, Israel Ben Guilherme Fonseca wrote:
>> Why the transaction is attached to the instance?
> just as a convenience, especially inside your model code.
The key point to keep in mind is that transactions are tied to /repositories/,
not models or instances. If all the models you are operating with are located
inside the same repository (specified in database.yml), then a new transaction
on that repository will apply to *all of them*.
So: AnyOfYourModel.transaction is equivalent to
AnyOfYourModel.repository.transaction is equivalent to
::DataMapper.repository(AnyOfYourModel.repository.name).transaction. If the
repository name is unspecified in your database.yml, OR if it is specified in
your database.yml and named "default", then ::DataMapper.repository.transaction
also works (because repository defaults to "default" name).
There are a few other ways to get at the transaction method for convenience,
but the key conceptual point to remember is that transactions are tied to
repositories (which, in an RDBMS/SQL context, is a database instance).
>> The "link" API is very
>> weird.
> I don't know what this is but I've never used it
I've never seen the link() usage, and I would definitely recommend avoiding it.
I use transactions heavily and have never seen it or needed it.
>> Wouldn't be nicier a global method to start/commit/rollback
>> transactions?And how can I force a rollback?
>
> AnyOfYourModel.transaction do |t|
> t.rollback
> end
Exceptions also result in a ROLLBACK:
begin
AnyOfYourModel.transaction do
do_stuff
if something_broke
raise some_exception
end
end
rescue some_exception
end
Also, any non-exceptional exit from a transactional block results in a COMMIT:
AnyOfYourModel.transaction do
next # leaves block immediately, calls commit
return # due to a special hack in the code, this too exits the block
and calls commit
end
And finally, if you're using MySQL or PostgreSQL, as of 1.1 you can use nested
transactions within the same repository (just nest transaction blocks, and
after the first one, SAVEPOINTs will be employed instead).
cheers,
--jordan
--
You received this message because you are subscribed to the Google Groups
"DataMapper" group.
To post to this group, send email to [email protected].
To unsubscribe from this group, send email to
[email protected].
For more options, visit this group at
http://groups.google.com/group/datamapper?hl=en.
