Re: getting unique id

On Wed, Nov 23, 2022 at 3:11 PM Larry Martell <larry.martell@gmail.com> wrote:
>
> On Wed, Nov 23, 2022 at 3:01 PM Thomas Lockhart <tlockhart1976@gmail.com> wrote:
> >
> > Why not use the existing Django AutoField?
>
> Because I have multiple rows with the same batch_id, and also I would
> like the batch_ids to be sequential.
>
> The use case is a batch job dashboard. Users run jobs that spawn many
> sub jobs. The jobs all record their status in the JobStatus table. The
> batch dashboard shows all the sub jobs grouped under their parent job.
> The parent job creates a row with a new batch_id, and that is passed
> to the sub jobs. They all record their status using that same batch
> id, but each in its own row.
>
> > > On Nov 23, 2022, at 8:56 AM, Larry Martell <larry.martell@gmail.com> wrote:
> > >
> > > I have an app that needs to get a unique ID. Many threads run at the
> > > same time that need one. I would like the IDs to be sequential. When I
> > > need a unique ID I do this:
> > >
> > > with transaction.atomic():
> > > max_batch_id =
> > > JobStatus.objects.select_for_update(nowait=False).aggregate(Max('batch_id'))
> > > json_dict['batch_id'] = max_batch_id['batch_id__max'] + 1
> > > status_row = JobStatus(**json_dict)
> > > status_row.save()
> > >
> > > But multiple jobs are getting the same ID. Why does the code not work
> > > as I expect? What is a better way to accomplish what I need?

I ended up using another table to get the batch_ids from. It works,
but I still wonder how to make it work without a second table.

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