To finish this thread, I have decided to abandon the attempt. My
solution is to tell the users to avoid doing real work on the staging
server. It exists only to check out new features.
I feel better now.
Thanks Melvyn and Tim
Mike
On 10/11/2016 11:08 AM, Mike Dewhirst wrote:
> On 10/11/2016 12:06 AM, Tim Graham wrote:
>> I see. Although I would be interested to see what you come up with,
> @Tim
> It is getting there so if you are really interested I'll post it
> somewhere when it is working. I'm getting router errors at the moment
> which I might be able to workaround by permitting null in a FK fields
> during obj.save(using=db). Might ask some questions on this later. I
> don't really want to permit null in this particular case.
>
>> my initial reaction is that we wouldn't accept a patch for Django to
>> do this. It seems too complex and brittle.
>
> Having done some work on this I agree with you but disagree with Melvyn.
>
> The task is complex and would be almost impossible to generalise. For
> example, from a number of substances the user may have done serious
> work on only a few and won't want the others transferred.
>
> So I'm building a facility to transfer one substance at a time. If
> there is a future requirement for bulk transfer I can iterate.
>
> The transferred substance might be a mixture in which case I have to
> collect the ingredient substances plus the m2m through records which
> are effectively the recipe. Some of the ingredients might themselves
> be mixtures. Not worrying about that at the moment.
>
> For each substance there are 6 OneToMany, up to 15 OneToOne and two
> m2m relationships plus a OneToOne where the sibling has lots of its
> own complex relationships including a recursive OneToOne to form a
> daisy-chain of history. I'm skipping that one for the moment.
>
>> I agree with Melvyn
>
> See below
>
>> that it seems unusual to use Django's multi-database facilities to
>> transfer data between staging and production.
>>
>> On Wednesday, November 9, 2016 at 4:51:39 AM UTC-5, Melvyn Sopacua
>> wrote:
>>
>> On Wednesday 09 November 2016 13:59:35 Mike Dewhirst wrote:
>> > On 9/11/2016 9:13 AM, Tim Graham wrote:
>> > > Interesting idea. I'd be interested to here more about the use
>> case.
>> >
>> > Simple. I permitted my users to "play" on the staging site and
>> now one
>> > of them wants to transfer their work to the production site.
>>
>> Your approach is wrong. You think of this as one django project and
>> trying to cheat under the hood, while in fact they are two different
>> projects. And by design, staging is not always structually
>> identical to
>> production.
>>
>
> @Melvyn
>
> I was wrong to think saveasnew might do the trick.
>
> However, migration is fully implemented so I can easily abort any
> transfer if the structures are not identical. As it happens, there are
> only two databases at the moment. Staging and production and while
> they are not always structurally identical they are currently the same
> during testing.
>
>>
>> Your best approach is to use serialization with natural keys
>
> Maybe but the complexity and a couple of business rules persuade me to
> write code to do it "manually" so I can unit test it. Also, if I get
> it going, the user can select a substance to transfer and doesn't have
> to bother me.
>
> I also realise it is very brittle so it needs to be revised if the
> structure changes.
>
> Thanks for your advice. I appreciate it even if I think I need to
> tackle the problem my way.
>
> Cheers
>
> Mike
>
>> and a job
>> scheduler. Cron will do, but there's plenty other schemes allowing
>> you
>> to provide feedback about the job queue and expected time of
>> completion.
>> -- Melvyn Sopacua
>>
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