That's the approach I've used: either have a migration operation that you
can run (included in a 3rd party or local app), or a management command
that generates a migration file with the relevant custom operations.
Matt.
On Friday, August 28, 2015 at 11:37:55 AM UTC+9:30, Andrew Godwin wrote:
>
> Hi Gavin,
>
> Hooking into the migration autodetector is currently not really possible -
> it's quite inextensible, which is something I'd love to get ironed out in
> the long term but isn't really possible right now to modify it from
> third-party code.
>
> You can, however, supply custom migration Operation classes that people
> could put into their migrations manually, or potentially have some other
> way of outputting those migration files with operations in them (a lot of
> the code to write them out is re-useable). Hopefully someone else has a
> better idea!
>
> Andrew
>
> On Thu, Aug 27, 2015 at 6:27 PM, Gavin Wahl <gavi...@gmail.com
> <javascript:>> wrote:
>
>> I'm interested in writing a third-party app that allows users to
>> declaratively write check constraints and have them automatically be added
>> and removed by migrations. I'm envisioning being able to attach a list of Q
>> objects to your model, something like:
>>
>>
>> class Meta:
>> checks = [
>> Q(end_date__isnull=True) | Q(end_date__gt=F('start_date'))
>> ]
>>
>> Now that we have migrations, formalized Meta, and custom lookups, is it
>> possible for a third-party app to manage this seamlessly?
>>
>> I'm having trouble figuring out where it could hook in to migrations to
>> detect changes to the check constraints, and automatically generate the
>> migrations with operations to update the constraints. What code I should be
>> reading to figure out how to do it?
>>
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