[Django] #34803: Nested OuterRef can raise AttributeError: 'OuterRef' object has no attribute 'contains_over

Django

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Aug 29, 2023, 9:07:04 AM8/29/23

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#34803: Nested OuterRef can raise AttributeError: 'OuterRef' object has no
attribute 'contains_over_clause'
-------------------------------------+-------------------------------------
Reporter: | Owner: nobody
pierrenicolasr |
Type: Bug | Status: new
Component: Database | Version: 4.2
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
-------------------------------------+-------------------------------------
Porting our application from Django 3 to 4, we're seeing exception raised
in complex queries using nested OuterRef

{{{
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/query.py", line 1436, in filter
return self._filter_or_exclude(False, args, kwargs)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/query.py", line 1454, in _filter_or_exclude
clone._filter_or_exclude_inplace(negate, args, kwargs)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/query.py", line 1461, in
_filter_or_exclude_inplace
self._query.add_q(Q(*args, **kwargs))
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/query.py", line 1545, in add_q
clause, _ = self._add_q(q_object, self.used_aliases)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/query.py", line 1576, in _add_q
child_clause, needed_inner = self.build_filter(
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/query.py", line 1435, in build_filter
value = self.resolve_lookup_value(value, can_reuse, allow_joins)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/query.py", line 1204, in
resolve_lookup_value
value = value.resolve_expression(
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/query.py", line 1923, in resolve_expression
query = self.query.resolve_expression(*args, **kwargs)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/query.py", line 1145, in resolve_expression
clone.where.resolve_expression(query, *args, **kwargs)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/where.py", line 278, in resolve_expression
clone._resolve_node(clone, *args, **kwargs)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/where.py", line 270, in _resolve_node
cls._resolve_node(child, query, *args, **kwargs)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/where.py", line 274, in _resolve_node
node.rhs = cls._resolve_leaf(node.rhs, query, *args, **kwargs)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/sql/where.py", line 263, in _resolve_leaf
expr = expr.resolve_expression(query, *args, **kwargs)
File "/usr/local/filewave/python/lib/python3.10/site-
packages/django/db/models/expressions.py", line 862, in resolve_expression
if col.contains_over_clause:
AttributeError: 'OuterRef' object has no attribute 'contains_over_clause'
}}}

Looking at code, the issue seems to be the following:
{{{
class ResolvedOuterRef(F):
"""
An object that contains a reference to an outer query.

In this case, the reference to the outer query has been resolved
because
the inner query has been used as a subquery.
"""

contains_aggregate = False
contains_over_clause = False

def as_sql(self, *args, **kwargs):
raise ValueError(
"This queryset contains a reference to an outer query and may
"
"only be used in a subquery."
)

def resolve_expression(self, *args, **kwargs):
col = super().resolve_expression(*args, **kwargs)
if col.contains_over_clause:
raise NotSupportedError(
f"Referencing outer query window expression is not
supported: "
f"{self.name}."
)
}}}

In case of OuterRef(OuterRef( "field" )), `col =
super().resolve_expression(*args, **kwargs)` will use:
{{{
class OuterRef(F):
contains_aggregate = False

def resolve_expression(self, *args, **kwargs):
if isinstance(self.name, self.__class__):
return self.name
return ResolvedOuterRef(self.name)
}}}
so self.name is an OuterRef, then it returns it directly, and then ` if
col.contains_over_clause:` fails because col.contains_over_clause is not
defined for OuterRef.

Looks like adding col.contains_over_clause=False to class OuterRef solves
the issue - or checking if object col.contains_over_clause.

--
Ticket URL: <https://code.djangoproject.com/ticket/34803>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

Django

unread,

Aug 29, 2023, 9:22:50 AM8/29/23

to django-...@googlegroups.com

#34803: Nested OuterRef can raise AttributeError: 'OuterRef' object has no
attribute 'contains_over_clause'
-------------------------------------+-------------------------------------

Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------

Description changed by pierrenicolasr:

Old description:

New description:

Porting our application from Django 3 to 4, we're seeing exception raised
in complex queries using nested OuterRef

{{{
File "/usr/local/python/lib/python3.10/site-

packages/django/db/models/query.py", line 1436, in filter
return self._filter_or_exclude(False, args, kwargs)