#34594: KT doesn’t work across foreign keys
-------------------------------------+-------------------------------------
Reporter: Roman | Owner: nobody
Odaisky |
Type: Bug | Status: new
Component: Database | Version: 4.2
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
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Assuming
{{{
class Parent(Model):
data = JSONField()
class Child(Model):
parent = ForeignKey(Parent)
}}}
the expressions
{{{
Parent.objects.annotate(x=F("data__some_string")).first().x
Parent.objects.annotate(x=KT("data__some_string")).first().x
Parent.objects.first().data["some_string"]
}}}
all return the same value. So far, so good. However, in the following F
works but KT doesn’t:
{{{
Child.objects.annotate(x=F("parent__data__some_string"))
Child.objects.annotate(x=KT("parent__data__some_string"))
}}}
The problem is in the SQL that KT generates: `("parent"."id" #>>
ARRAY['data','some_string']) AS "x"`, which, it seems, is the result of
KeyTextTransform.from_lookup taking all the double-underscore-separated
parts of the argument of KT to mean JSON lookups and not other possible
lookups such as foreign keys.
Please fix by using the same mechanisms F uses in this case.
--
Ticket URL: <https://code.djangoproject.com/ticket/34594>
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