#34890: Migration can produce duplicate entries of UUID4 values for unique
fields
-------------------------------------+-------------------------------------
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 |
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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/>
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