#25265: DB Backend cannot specify query class.
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Reporter: techdragon | Owner: nobody
Type: New feature | Status: new
Component: Database layer | Version: master
(models, ORM) |
Severity: Normal | Resolution:
Keywords: | Triage Stage: Accepted
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Comment (by akaariai):
Its also worth noting that there are three ways to implement nonsql
backends:
1. Implement Compiler
2. Implement Query (and possibly Compiler)
3. Implement QuerySet (and possibly Query and Compiler)
Currently implementing a different Compiler for nonsql backend is the
suggested approach. In principle it should work. In practice, I don't
know. I guess the biggest problem is that when doing this, the author is
targeting an often changing internal API.
I'm not sure implementing Query is that much better. The API for Query
isn't public. How about implementing QuerySet itself? Now that iterator is
separated from QuerySet, it isn't that much more work when compared to
just implementing Query and/or Compiler.
For .using() incompatibility - I think we should throw an error. And the
default backend should be used to decide what is the default queryset
type. So, if you have default db = mongodb, other = postgres, then
User.objects.filter(foo=bar).using('other') should throw an error, but
User.objects.using('other').filter(foo=bar) shouldn't.
It is also worth noting that maybe the right answer is to use different
*models* altogether - Django's default user, permission and groups system
for example isn't a good design for non-relational databases. If you
control the models, then you also control the default queryset type, and
we don't have a problem to begin with.
I guess I am +½ to manager .get_queryset() checking the query/queryset
class from the default backend, with the idea that objects.using('other')
will get you the other backend's query/queryset class.
Finally, I think whatever we come up with here, we should present the
solution on django-developers and ask for opinions.
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Ticket URL: <https://code.djangoproject.com/ticket/25265#comment:4>
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