[Django] #34890: Migration can produce duplicate entries of UUID4 values for unique fields
Django
-------------------------------------+-------------------------------------
Reporter: | Owner: nobody
makisukurisu |
Type: | Status: new
Uncategorized |
Component: Database | Version: 3.2
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 |
-------------------------------------+-------------------------------------
Hello, I've run into the following problem.
When adding a new field, with UUID-4 generator (if I can say so),
migration fails on a larger dataset of my testing environment.
I get this error:
{{{
Running migrations:
Applying ***_module.***_migration_name...Traceback (most recent call
last):
File "***/python/lib/python3.10/site-
packages/django/db/backends/utils.py", line 84, in _execute
return self.cursor.execute(sql, params)
File "***/python/lib/python3.10/site-
packages/django/db/backends/mysql/base.py", line 73, in execute
return self.cursor.execute(query, args)
File "***/python/lib/python3.10/site-packages/MySQLdb/cursors.py", line
206, in execute
res = self._query(query)
File "***/python/lib/python3.10/site-packages/MySQLdb/cursors.py", line
319, in _query
db.query(q)
File "***/python/lib/python3.10/site-packages/MySQLdb/connections.py",
line 254, in query
_mysql.connection.query(self, query)
MySQLdb.IntegrityError: (1062, "Duplicate entry
'd278f389a95b47b2aaea6fdb5e14d6a4' for key 'external_id'")
}}}
The field itself looks like:
{{{
class SomeModel(BaseModel):
external_id = models.UUIDField(default=uuid.uuid4, editable=False,
unique=True)
#...
}}}
And finally, migration code looks like this:
{{{
# Generated by Django 3.2 on 2023-10-04 08:37
from django.db import migrations, models
import uuid
class Migration(migrations.Migration):
dependencies = [
('module_name', 'migration_name_and_number'),
]
operations = [
migrations.AddField(
model_name='SomeModel',
name='external_id',
field=models.UUIDField(default=uuid.uuid4, editable=False,
unique=True),
),
]
}}}
Since this is a new field, there's no possibility of collision to happen
with previous values. This leads me to conclude, there's a problem with
either concurrent requests, that result in Integrity error, or some other
error in code that applies migrations.
As you can see – I use MySQL database backend, and Python3.10.
In local this migration is applied just fine, because there's way smaller
dataset (we are comparing 2800 and 10 records in the database).
Please advise, if there's some known fix for the issue, or a possible
workaround. Thank you!
If you need some additional information, please let me know, I'll gladly
provide it.
''P.S. I've noticed that the value shown in the exception is not exactly a
UUID-4 string, is this expected?''
--
Ticket URL: <https://code.djangoproject.com/ticket/34890>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.
Django
-------------------------------------+-------------------------------------
Type: Uncategorized | Status: closed
Component: Database layer | Version: 3.2
(models, ORM) |
Severity: Normal | Resolution: invalid
Keywords: | Triage Stage:
| Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-------------------------------------+-------------------------------------
* status: new => closed
* resolution: => invalid
Comment:
Hi there,
Unfortunately you haven't supplied enough information to confirm this is a
bug with Django. You've mentioned this is from adding a new field yet
there's data violating the unique constraint there. You may need to work
through the issue further to isolate the source of the conflict. If you
need help you can jump on the forum or Discord to request help from a
friendly community member: https://www.djangoproject.com/community/
(Additionally you will also need to confirm this is an issue with the
latest version of Django before continuing – Django 3.2 is only receiving
security patches)
If you do confirm there is an issue please feel free to reopen this
ticket.
Good luck!
--
Ticket URL: <https://code.djangoproject.com/ticket/34890#comment:1>