In Django the normal behavior should be that when you do a save() it will
automatically commit() your query's to the database.
so that in obj.save() you should just could access the pk with obj.id after
you did a obj.save().
If you want to maybe stop the commit you need to do a obj =
obj.save(commit=False), then you could add some things to your obj and
commit/save it later.
But as i understood you already do a obj.save() but it doesn't commit
correctly? Maybe you should just try a PostgreSQL database for testing,
since I'm not having trouble looking up objects after i saved it.
I often do things like:
obj.save()
return HttpResponseRedirect(reverse('view', {'pk': obj.id}))
and i never run into any exception
Am Dienstag, 21. Mai 2013 23:20:53 UTC+2 schrieb Chris Conover:
>
> Calling transaction.commit() after object.save results in
> a TransactionManagementError. I mentioned at the end that I am using MySQL
> (5.5.27). The issue is not that the Gearman workers are having trouble
> saving their transactions, it's that they are having trouble looking up the
> incoming object. I'm assuming the view and workers are separate
> transactions since I don't see how they could be connected -- though I'm
> looking into this.
>
> On Tuesday, May 21, 2013 1:05:54 PM UTC-4, Tom Evans wrote:
>>
>> On Tue, May 21, 2013 at 4:23 PM, Chris Conover <[email protected]> wrote:
>> > Hello,
>> >
>> > I'm having an issue looking up objects immediately after they are saved
>> and
>> > am wondering if anyone has any advice on how to address the problem.
>> > Specifically, I'm saving an object in a view (nothing fancy, a simple
>> > save()) and then kicking off a Gearman task to do some operations on
>> that
>> > saved object in the background. I pass the newly created object's PK as
>> data
>> > to the Gearman worker which then does a simple
>> Objects.objects.get(pk=PK).
>> > However, almost all of the time this lookup operation fails with an
>> > DoesNotExist exception. I believe the problem has to do with
>> transactions.
>> > Namely, the read in the Gearman worker is happening before the write
>> from
>> > the view is committed to the database. I've tried several things
>> including
>> > refactoring the saving code to be wrapped in a
>> > @transaction.commit_on_success block, moving the worker submission to
>> > post_save and adding a long delay before the Gearman worker does the
>> lookup.
>> > Nothing really seems to solve the problem completely. Even with a 60
>> second
>> > delay, the lookup fails with some frequency. Am I missing something
>> here? Is
>> > there some Django query cache that I can clear? Or should I just
>> rewrite all
>> > this to just to use a look-back perspective.
>> >
>> > The stack is Django 1.4 connecting to MySQL 5.5.27. Django is handling
>> > 200-1000 requests per second and the database is handling about double
>> that.
>> >
>> > Thanks,
>> > Chris
>>
>> from django import transaction
>> …
>> obj.save()
>> transaction.commit()
>> task.submit(obj.id)
>>
>> You will also need to make sure that gearman is doing things correctly
>> as well. You haven't mentioned what database you are using, but if
>> gearman's DB connection is in a read repeated mode, you can do
>> whatever you like in django but you won't see new data in gearman
>> until gearman's current transaction is committed.
>>
>> Cheers
>>
>> Tom
>>
>
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