[Django] #36449: Mismatched fields in composite primary key ForeignObject example model

[Django]

#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              |
-----------------------------------------+-----------------------------
 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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