#36449: Mismatched fields in composite primary key ForeignObject example model
-----------------------------------------+-----------------------------
Reporter: Jacob Walls | Owner: Jacob Walls
Type: Bug | Status: assigned
Component: Documentation | Version: 5.2
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 1
UI/UX: 0 |
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The field types on [https://docs.djangoproject.com/en/5.2/topics
/composite-primary-key/#composite-primary-keys-and-relations this example
model] are not correct; the primary key of `Order` is CharField, and
`Product` is IntegerField:
{{{#!py
class Foo(models.Model):
item_order_id = models.IntegerField()
item_product_id = models.CharField(max_length=20)
item = models.ForeignObject(
OrderLineItem,
on_delete=models.CASCADE,
from_fields=("item_order_id", "item_product_id"),
to_fields=("order_id", "product_id"),
)
}}}
It should be:
{{{#!py
class Foo(models.Model):
item_order_id = models.CharField(max_length=20)
item_product_id = models.IntegerField()
item = models.ForeignObject(
OrderLineItem,
on_delete=models.CASCADE,
from_fields=("item_order_id", "item_product_id"),
to_fields=("order_id", "product_id"),
)
}}}
Found this while trying to write a test with these models, e.g. this
fails:
{{{#!py
In [28]: f = Foo.objects.first()
In [29]: f.item
Out[29]: <OrderLineItem: OrderLineItem object ((1, '1'))>
In [30]: Foo.objects.filter(item=item)
Out[30]:
---------------------------------------------------------------------------
UndefinedFunction Traceback (most recent call
last)
File ~/django/django/db/backends/utils.py:105, in
CursorWrapper._execute(self, sql, params, *ignored_wrapper_args)
104 else:
--> 105 return self.cursor.execute(sql, params)
UndefinedFunction: operator does not exist: character varying = integer
LINE 1: ...."item_order_id", "models_foo"."item_product_id") = ('1', 1)...
^
HINT: No operator matches the given name and argument types. You might
need to add explicit type casts.
}}}
----
While here, also suggest documenting inside the caveats about how
`ForeignObject` differs from `ForeignKey` that the `on_delete` argument is
ignored.
--
Ticket URL: <https://code.djangoproject.com/ticket/36449>
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