QuerySet crashes when nested OuterRef is combined with an operator or used in function.

[Ben Nace]

Given the following contrived set of models and the latest Django 3.0.5:

class Node(models.Model):
    steplen = 4
    path = models.CharField(max_length=100)


class NodeAttribute(models.Model):
    node = models.ForeignKey(Node, on_delete=models.CASCADE)
    attribute_name = models.CharField(max_length=64)
    attribute_value = models.CharField(max_length=64)


class Entity(models.Model):
    name = models.CharField(max_length=64)
    age = models.IntegerField()


class EntityNode(models.Model):
    entity = models.ForeignKey(Entity, on_delete=models.CASCADE)
    node = models.ForeignKey(Node, on_delete=models.CASCADE)
    role = models.CharField(max_length=64)

The query

NodeAttribute.objects.annotate(
    test=Subquery(Entity.objects.filter(
        entitynode__node__nodeattribute__attribute_name=OuterRef('attribute_name'), 
        name=Subquery(EntityNode.objects.filter(
            node__path=Left(OuterRef(OuterRef('node__path')), Node.steplen * 2)
        ).values('entity__name')[:1])
    ).values('age')[:1])
)

produces the exception "AttributeError: 'OuterRef' object has no attribute 'relabeled_clone'."

The problem is with using nested OuterRefs as a parameter to Left. I have not had any trouble with using a single OuterRef with SQL functions, but trying to go up two levels with nested OuterRefs does not appear to work. Please note that the above models and query are for illustrative purposes only and represent the simplest example of the problem I could come up with.

[Simon Charette]

Pretty sure this is a duplicate of #29214 (see comment:12). Just like F the OuterRef expression doesn't support __ join references, the fact Left and nested OuterRef are used here are unrelated I believe.

[Ben Nace]

Replying to Simon Charette:

Pretty sure this is a duplicate of #29214 (see comment:12). Just like F the OuterRef expression doesn't support __ join references, the fact Left and nested OuterRef are used here are unrelated I believe.

#29214 comment:12 refers to joins inside F in UPDATE queries, not in general. The ​documentation states

You can also use the double underscore notation to span relationships in an F() object. An F() object with a double underscore will introduce any joins needed to access the related object.

[Simon Charette]

Sorry my mistake, I misread the ticket description and thought this was about update as well.

Could you try simply adding this method to OuteRef and see if it addresses your crash?

django/db/models/expressions.py

@@ -581 +581 @@
             return self.name
         return ResolvedOuterRef(self.name)
 
+    def relabeled_clone(self, relabels):
+        return self
+
 
 class Func(SQLiteNumericMixin, Expression):
     """An SQL function call."""

[Mariusz Felisiak]

Adding OuterRef.relabeled_clone() fix this issue for me. It's not related with join references, you can easily reproduce it by combining nested OuterRef() with an operator, e.g. Time.objects.filter(time__lt=OuterRef(OuterRef('time')) * 2).

Related with #29142.

[Hasan Ramezani]

​PR

[Ben Nace]

I can confirm the proposed patch fixes it for me too.

[Mariusz Felisiak <felisiak.mariusz@…>]

In 6fbce45:

Fixed #31415 -- Fixed crash when nested OuterRef is used with operators or in database functions.