#30564: Cannot create custom field that returns a queryset AND uses pre_save().
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Reporter: Dan J Strohl | Owner: nobody
Type: Bug | Status: new
Component: Database layer | Version: master
(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
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Comment (by Simon Charette):
> The issue is that by using if hasattr(value, 'resolve_expression'), you
cannot deterministically tell the difference between a SQL expression and
a Django QuerySet.
FWIW even if the `QuerySet` class doesn't completely implement the
expression API it partially behaves like one; that's what makes usage of
`QuerySet` as subqueries work (e.g.
`.filter(foo__in=Foo.objects.filter(bar=1))`. In that sense `QuerySet` is
an SQL expression.
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Ticket URL: <https://code.djangoproject.com/ticket/30564#comment:4>
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