How to optimize Django ORM to use outer join instead of subquery when self-referencing fields?

Using Django Using the ORM
1 
org_id = attrs.get('organization_id')
person_name = attrs.get('name', getattr(self.instance, 'name', None))

existing_entries = LeadModel.objects.filter(
    role='manager',
    organization_id=org_id,
    is_converted=True
)
if self.instance:
    # Exclude current instance in case of update
    existing_entries = existing_entries.exclude(id=self.instance.id)

if existing_entries.exists():
    raise serializers.ValidationError({
        "message": "A manager already exists for this organization. You cannot create a new one."
    })

try:
    org_data = LeadModel.objects.get(unique_id=org_id)
    if not org_data.owner_name or org_data.owner_name.strip().lower() != person_name.strip().lower():
        org_data.owner_name = person_name
        org_data.save(update_fields=['owner_name'])
except ObjectDoesNotExist:
    pass

return attrs
2

Hello there,

You are unlikely to get an answer here without providing the queries that are causing you trouble and what you’d like them to look like.

From what I can see there should be not use of subqueries here as exclude will only use them when filtering against multi-valued relationships

All I can see in terms of queries here are

SELECT 1
FROM leadmodel
WHERE
    role = 'manager'
    AND organization_id = ?
    AND is_converted
    AND NOT (id = ?)
LIMIT 1
---
SELECT * FROM leadmodel WHERE id = ?
---
UPDATE leadmodel SET owner_name = ? WHERE id = ?

by the way it looks it looks like you re-implemented exactly what a conditional unique constraint on LeadManager would have achieved by itself

class LeadManager(models.Model):
    ...
    class Meta:
        constraints = [
            UniqueConstraint(
                fields=["organization_id"],
                condition=Q(role="manager", is_converted=True),
            )
        ]