#36911: bulk_update() incorrectly allows updating GeneratedField (silent
failure on
SQLite)
-------------------------------------+-------------------------------------
Reporter: jaffar Khan | Type: Bug
Status: new | Component: Database
| layer (models, ORM)
Version: dev | Severity: Normal
Keywords: bulk_update | Triage Stage:
GeneratedField | Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
Currently, bulk_update() does not validate if the fields provided in the
fields=[...] argument are GeneratedField instances.
Model:
{{{
class Product(models.Model):
price = models.IntegerField()
quantity = models.IntegerField()
total = models.GeneratedField(
expression=models.F("price") * models.F("quantity"),
output_field=models.IntegerField(),
db_persist=True,
)
}}}
test function:
{{{
def run_test():
# Create product
p = Product.objects.create(price=10, quantity=2)
p.total = 9999
try:
Product.objects.bulk_update([p], fields=["total"])
print("silent failure")
except Exception as e:
print(f"CRASH: {e}")
}}}
output:
**silent failure**
If a developer accidentally includes a **GeneratedField** in
**bulk_update()**, Django attempts to include it in the SQL UPDATE
statement.
On SQLite, this results in a silent failure (no error is raised, but the
value is obviously not updated as it is generated).
On strict databases (like PostgreSQL), this likely results in an
OperationalError.
Django should raise a FieldError immediately when **bulk_update()** is
called with a **GeneratedField**, similar to how it handles other read-
only fields or invalid field names.
--
Ticket URL: <https://code.djangoproject.com/ticket/36911>
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