Combined queryset crash when chaining `values()` after `order_by()` with annotated constants.

[GardenLee]

When I tried query with 'annotate', 'union', 'order_by('annotate_field')' and 'values' at the same time, i got AttributeError('NoneType' object has no attribute 'split')

ex)
# 1. make 2 QuerySets

qs1 = Foo.objects.annotate(bar_val=Value(1, output_field=IntegerField())).filter(bar=False)
qs2 = Foo.objects.annotate(bar_val=Value(2, output_field=IntegerField())).filter(bar=True)

# 2. union

qs3 = qs1.union(qs2)

# 3. order_by annotate field

qs4 = qs3.order_by('bar_val')

# 4. get values

qs4.values('id')

In this case, I confirmed ('id', None) tuple passed by compiler.query.set_values() in django/db/models/sql/compiler.py

[Mariusz Felisiak]

Thanks for this ticket. This code was changed in 2cbd3967e0a51eab993df89679046d25ec78baec, however previously it raised DatabaseError so IMO it's not a release blocker. We can consider backporting if patch will be straightforward.

[Hasan Ramezani]

I take a look and here is my understanding:

In this case, when we order queryset by annotated value(bar_val) the ​src variable, has type <class 'django.db.models.functions.comparison.Cast'> and src.output_field.name is None.
So, ​add_select_col function adds None to values_select.

we should somehow add bar_val to the values_select.

@felixxm, If you have any workaround, I can prepare a patch.

[David Wobrock]

Hi,

Suggested patch: ​https://github.com/django/django/pull/13503
which probably needs some improvements here and there to be more concise and sustainable :)

Thanks!
David