#30490: migrations unique_index on (app, name)
-------------------------------------+-------------------------------------
Reporter: | Owner: nobody
rkojedzinszky |
Type: Bug | Status: new
Component: | Version: 1.11
Uncategorized | Keywords: migrations parallel
Severity: Normal | run
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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I've a django based api service. I run it in containers, in kubernetes.
When I update my image, basically I run the migiration process, then start
the application. With k8s for example, when I start the deployment with 2
or more replicas, actually 2 parallel running migration process will
start. With the following very simple migration process, unfortunately the
migration will be applied twice:
{{{
from django.db import migrations
from django.db.models import F
import time
def forward(apps, schema_editor):
TT = apps.get_model('center', 'TestTable')
time.sleep(10)
TT.objects.all().update(value=F('value') + 1)
def backward(apps, schema_editor):
TT = apps.get_model('center', 'TestTable')
TT.objects.all().update(value=F('value') - 1)
class Migration(migrations.Migration):
dependencies = [
('center', '0007_testtable'),
]
operations = [
migrations.RunPython(forward, backward)
]
}}}
Even if the migration process is ran in a transaction, due to the unique
index missing, it will be applied multiple times.
Even though my setup may be rare, I think it would really be necessary to
prevent migrations to be applied more than once. Db unique_together could
be utilized for that.
--
Ticket URL: <https://code.djangoproject.com/ticket/30490>
Django <https://code.djangoproject.com/>
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