Support ordering by annotation transforms (e.g JSONObject/ArrayAgg transforms).

[Eugene Morozov]

Please see the example:

queryset = Model.objects.all().annotate(
    json_field=functions.JSONObject(
        test_pk=models.Value(100) + models.F("pk"),
    ),
    test_pk_from_json_field=models.F("json_field__test_pk"),
)
print(queryset.order_by("json_field__test_pk"))  # AttributeError: 'JSONField' object has no attribute 'model'
print(queryset.order_by("test_pk_from_json_field"))  # Successful

Full traceback for ordering by json_field__test_pk:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/local/lib/python3.10/site-packages/django/db/models/query.py", line 256, in __repr__
    data = list(self[:REPR_OUTPUT_SIZE + 1])
  File "/usr/local/lib/python3.10/site-packages/django/db/models/query.py", line 280, in __iter__
    self._fetch_all()
  File "/usr/local/lib/python3.10/site-packages/django/db/models/query.py", line 1324, in _fetch_all
    self._result_cache = list(self._iterable_class(self))
  File "/usr/local/lib/python3.10/site-packages/django/db/models/query.py", line 51, in __iter__
    results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
  File "/usr/local/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 1162, in execute_sql
    sql, params = self.as_sql()
  File "/usr/local/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 513, in as_sql
    extra_select, order_by, group_by = self.pre_sql_setup()
  File "/usr/local/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 56, in pre_sql_setup
    order_by = self.get_order_by()
  File "/usr/local/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 356, in get_order_by
    order_by.extend(self.find_ordering_name(
  File "/usr/local/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 769, in find_ordering_name
    return [(OrderBy(transform_function(t, alias), descending=descending), False) for t in targets]
  File "/usr/local/lib/python3.10/site-packages/django/db/models/sql/compiler.py", line 769, in <listcomp>
    return [(OrderBy(transform_function(t, alias), descending=descending), False) for t in targets]
  File "/usr/local/lib/python3.10/site-packages/django/db/models/sql/query.py", line 1666, in transform
    wrapped = previous(field, alias)
  File "/usr/local/lib/python3.10/site-packages/django/db/models/sql/query.py", line 1641, in final_transformer
    return field.get_col(alias)
  File "/usr/local/lib/python3.10/site-packages/django/db/models/fields/__init__.py", line 397, in get_col
    if alias != self.model._meta.db_table or output_field != self:
AttributeError: 'JSONField' object has no attribute 'model'

It seems there is a lack of support JSONField in order_by queryset.

[Mariusz Felisiak]

Thanks for the report. Tentatively accepted for an investigation, I'm not sure if it's feasible.

[Aman Pandey]

"It seems there is a lack of support JSONField in order_by queryset."
this is not true as JSONField based example queryset is working fine with order_by method

i guess it's more likely lack of support for lookup expression on annotated JSONObject

[Aman Pandey]

i think the issue is JSONObject returns a JSONField and since it's annotated JSONField doesn't get populated with the details of model it belongs to
since field generally are called in a model so they get populated with details of that model , here JSONField didn't get any details , including "self. model"
which causes an error .

so the main error occurs when order_by gets a lookup expression "" with double underscore , and by default it looks for an in relationship model's field which is populated by model's info but JSONField returned by JSONObject is not populated .thus throwing an error .

so ordey_by takes " " look up for models in relationship , that is what the syntax is meant for , it never meant to support this syntax for json elements
so should i close the ticket or try to work on it and change the status to feature

[Aman Pandey]

i was trying to populate the Model and freshly created JSONField with each other's info like trying to populate JSONField.model with model info and
model._meta with JSONField info while the execution of annotate-> order_by-> add_ordering ->names_to_path (where lookup is processed ) but

that approach is very naive and making me fall deeper.

[Rodolfo Valentín Becerra García]

Try this

from django.db.models.fields.json import KeyTextTransform
Model.objects.all().annotate(
    json_field=functions.JSONObject(
        test_pk=models.Value(100) + models.F("pk"),
    ),
    test_pk_from_json_field=KeyTextTransform(
        "test_pk", "json_field"
    )
)

[Saad Aleem]

Is this issue still valid? I'm trying to find a good first issue to create a PR for and did some digging here.

It looks like a model is attached to a Field object using the contribute_to_class method.

It seems that the contribute_to_class method is called when fields are added to the model class during its creation or when fields are added dynamically. In this case, we're not adding or modifying fields in the model class; we're only working with the queryset and computing new values based on existing fields. The queryset annotations do not modify the model class itself, so contribute_to_class is not called in this context.

[Eugene Morozov]

I haven't tested this problem with the latest versions of Django 4.2 and postgres 3. Nonetheless, I don't believe that the issue is linked to the modifications made in Django 4.2.

So, you can try to run the code from the example and I think it will be still not working.

[Saad Aleem]

Replying to Eugene Morozov:

I haven't tested this problem with the latest versions of Django 4.2 and postgres 3. Nonetheless, I don't believe that the issue is linked to the modifications made in Django 4.2.

So, you can try to run the code from the example and I think it will be still not working.

Thanks for the quick response.

I was able to reproduce it on the main branch but to fix it, a model would need to be attached to the JSONField inside the JSONObject method but it can't be done since annotations don't modify the model itself. So it seems like it might require a big architectural change for this to work.

[Mariusz Felisiak]

#35025 was a duplicate for ArrayField returned by ArrayAgg.

[Simon Charette]

Feels like this is more of a new feature than a bug after all since adding support for JSONObject key ordering required adding generic support for ordering by annotation transforms.

[Mariusz Felisiak <felisiak.mariusz@…>]

In b0ad4119:

Fixed #34013 -- Added QuerySet.order_by() support for annotation transforms.

Thanks Eugene Morozov and Ben Nace for the reports.

[GitHub <noreply@…>]

In eea4f92f:

Refs #34013 -- Registered instance lookups as documented in tests.