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Editorial Team
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Asked: 2026-05-31T14:59:36+00:00

Is Django or maybe POSTGRESQL losing information about primary keys and foreign keys when

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Is Django or maybe POSTGRESQL losing information about primary keys and foreign keys when you create a view which relates to a view which relates to a table, which has primary and foreign keys?

I have a View-A (all 3 fields are Foreign Keys) and that view gets 2 fields from a View-B. The View-B gets its fields from a table-C. table-C has primary key and foreign key.

So when i access View-A with my django model, how do i treat those fields? I know they are foreign keys, but any kind of filter results in a empty Queryset.
if i use something like

myview = viewA.objects.using(db).all()  # getting all the data
myview2= viewA.objects.using(db).all()[:5] # getting 5 objects

.

class viewA(models.Model):
class Meta:
    db_table = "viewA"

x = models.ForeignKey(x, primary_key=True)
y = models.ForeignKey(y)
z = models.ForeignKey(z)

The problem is that i can not filter!

response=viewA.objects.using(db).filter(y_id=1)  ERROR:= FieldError

Behind all those FK, there are integer/bigint fields.

Edit:
Since this are INNER JOINS i would like to access not only the fields from ViewA, but also from ViewB. x,y,z are from type ViewB. Maybe use select_related()?

So any clues if Django or postgres lose information about keys in views which relate to other views?

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1 Answer

  1. Editorial Team

    See my two comments; however, to answer your specific “query”.

    If you go to the docs, and see this paragraph:

    https://docs.djangoproject.com/en/dev/ref/models/fields/#database-representation

    You will note that foreign keys, by default, have the _id appended to their names. Now, there are occasions in which you need to access the column name directly and it’s a good idea to be aware of the column as a “bigger picture” sort of thing, but at as far as Model API is concerned, you should, when doing something against a foreign key, use the attribute name given in the model instance.

    Edit from your comment:

    If you want to drill down and filter against some field in the foreignkey object, you just do y__fieldname = somevalue

    Note that fieldname must be in the y object.

    If you are getting back and empty queryset, this is because nothing in that column matched the value you gave it.

    To test this, create a queryset directly on the “y” object and then try to do y.objects.fitler(fieldname=somevalue)

    if you still get back and empty queryset, you know that value doesn’t exist. Furthermore, you can look into the database and try a raw query in pgadminIII if you have that set up.

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