#32577: Add support for `UUIDAutoField` `DEFAULT_AUTO_FIELD`
-------------------------------------+-------------------------------------
Reporter: Tomasz Wójcik | Owner: nobody
Type: Uncategorized | Status: new
Component: Database layer | Version: 3.2
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Description changed by Tomasz Wójcik:
Old description:
> Default auto field introduced in #31007,
> [https://docs.djangoproject.com/en/3.2/releases/3.2/#customizing-type-of-
> auto-created-primary-keys as seen in the docs], is `BigAutoField`.
>
> {{{
>
> class BigAutoField(AutoFieldMixin, BigIntegerField):
> def get_internal_type(self):
> return 'BigAutoField'
>
> def rel_db_type(self, connection):
> return BigIntegerField().db_type(connection=connection)
>
> }}}
>
> Many projects prefer UUID field over big int for pk. So far we had to use
> a mixin for that but I am under the impression `DEFAULT_AUTO_FIELD`
> exists to lift this burden.
>
> I'd expect something like this to work (additional adjustments might be
> needed)
>
> {{{
>
> from django.db import models
> from django.db.models.fields import AutoFieldMixin
>
> class UUIDAutoField(AutoFieldMixin, models.UUIDField):
> def get_internal_type(self):
> return 'UUIDAutoField'
>
> def rel_db_type(self, connection):
> return models.UUIDField().db_type(connection=connection)
> }}}
>
> But if I use this for `DEFAULT_AUTO_FIELD` I get the error
>
> {{{
> ValueError: Primary key 'common.fields.UUIDAutoField' referred by
> DEFAULT_AUTO_FIELD must subclass AutoField.
> }}}
>
> I noticed two things I want to share.
>
> First, the default auto field `BigAutoField` is not subclassing
> `AutoField` so it's not consistent with the error message.
>
> Second, `AutoField` is subclassing `IntegerField`. If I understand this
> correctly, users are limited to subclass `IntegerField` for
> `DEFAULT_AUTO_FIELD`. If so, there's no way to implement `UUIDAutoField`
> as `DEFAULT_AUTO_FIELD`.
>
> I understand auto fields need to share a common interface but having to
> subclass `IntegerField` is a big constraint.
>
> I'm happy to open a PR once I know what's the desired functionality.
> Possible solutions I see:
> - enforce subclassing from `AutoFieldMixin` instead of `AutoField`
> - I don't think this field has to be very generic because DB pk types are
> very limited. As far as I know, only ints and UUIDs make sense for pk.
> Maybe adding `UUIDAutoField` to django fields would make sense. That way
> it'd have to enforce subclass of `AutoField` or `UUIDAutoField`
>
> Mentioned also in [https://groups.google.com/g/django-
> developers/c/MBPEPKlibGQ/m/uJVZbMpqBAAJ here],
> [https://groups.google.com/g/django-
> developers/c/MBPEPKlibGQ/m/ntEoLCCMBAAJ here] and
> [https://github.com/django/django/pull/13179#issuecomment-742473840
> here].
>
> {{{
> Django==3.2rc1
> }}}
New description:
Default auto field introduced in #31007,
[https://docs.djangoproject.com/en/3.2/releases/3.2/#customizing-type-of-
auto-created-primary-keys as seen in the docs], is `BigAutoField`.
{{{
class BigAutoField(AutoFieldMixin, BigIntegerField):
def get_internal_type(self):
return 'BigAutoField'
def rel_db_type(self, connection):
return BigIntegerField().db_type(connection=connection)
}}}
Many projects prefer UUID field over big int for pk. So far we had to use
a mixin for that but I am under the impression `DEFAULT_AUTO_FIELD` exists
to lift this burden.
I'd expect something like this to work (additional adjustments might be
needed)
{{{
from django.db import models
from django.db.models.fields import AutoFieldMixin
class UUIDAutoField(AutoFieldMixin, models.UUIDField):
def get_internal_type(self):
return 'UUIDAutoField'
def rel_db_type(self, connection):
return models.UUIDField().db_type(connection=connection)
}}}
But if I use this for `DEFAULT_AUTO_FIELD` I get the error
{{{
ValueError: Primary key 'common.fields.UUIDAutoField' referred by
DEFAULT_AUTO_FIELD must subclass AutoField.
}}}
I noticed two things I want to share.
First, the default auto field `BigAutoField` is not subclassing
`AutoField` so it's not consistent with the error message.
Second, `AutoField` is subclassing `IntegerField`. If I understand this
correctly, users are limited to subclass `IntegerField` for
`DEFAULT_AUTO_FIELD`. If so, there's no way to implement `UUIDAutoField`
as `DEFAULT_AUTO_FIELD`.
I understand auto fields need to share a common interface but having to
subclass `IntegerField` is a big constraint.
I'm happy to open a PR once I know what's the desired functionality.
Possible solutions I see:
- enforce subclassing of `AutoFieldMixin` instead `AutoField`
- I don't think this field has to be very generic because DBs pk types are
very limited. As far as I know, only ints and UUIDs make sense for pk.
Maybe adding `UUIDAutoField` to django fields would make sense. That way
it'd have to enforce subclass of `AutoField` or `UUIDAutoField`
Mentioned also in [https://groups.google.com/g/django-
developers/c/MBPEPKlibGQ/m/uJVZbMpqBAAJ here],
[https://groups.google.com/g/django-
developers/c/MBPEPKlibGQ/m/ntEoLCCMBAAJ here] and
[https://github.com/django/django/pull/13179#issuecomment-742473840 here].
{{{
Django==3.2rc1
}}}
--
--
Ticket URL: <https://code.djangoproject.com/ticket/32577#comment:2>
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