#30431: Migration hangs on non default database
-------------------------------------+-------------------------------------
     Reporter:  mandm                |                    Owner:  nobody
         Type:  Bug                  |                   Status:  new
    Component:  Migrations           |                  Version:  1.11
     Severity:  Normal               |               Resolution:
     Keywords:  migrations, uuid,    |             Triage Stage:
  uuidfield, database router,        |  Unreviewed
  multiple database                  |
    Has patch:  0                    |      Needs documentation:  0
  Needs tests:  0                    |  Patch needs improvement:  0
Easy pickings:  0                    |                    UI/UX:  0
-------------------------------------+-------------------------------------
Description changed by mandm:

Old description:

> I'm trying to add a UUIDField in an existing user model following this
> method (with unique=True & default=uuid.uuid4).
> https://docs.djangoproject.com/en/1.11/howto/writing-migrations
> /#migrations-that-add-unique-fields
>
> This works with a single database but hangs in the following scenarios
> with multiple databases :
>
> - Hangs ! Migration with option `--database=foobar`
> - Hangs ! Migration without option `--database=foobar`, but with
> `using('foobar')` in the query in gen_uuid function
> - Works ! Migration without option `--database=foobar`
>

> Here's a snippet of the code I've used. I would be glad to provide
> additional information to reproduce the issue.
>
> User model :
>
> {{{
> class CustomUser(AbstractUser):
>     address = models.TextField()
>     uniq_id = models.UUIDField(unique=True, default=uuid.uuid4)
>
>     class Meta:
>         db_table = 'customuser'
> }}}
>

> Migration file
>

> {{{
> def gen_uuid(apps, schema_editor):
>     UserModel = apps.get_model('myapp', 'customuser')
>     for row in UserModel.objects.all():     #
> .objects.using('foobar').all(): -- HANGS !
>         row.uniq_id = uuid.uuid4()
>         row.save(update_fields=['uniq_id']) # .save(using='foobar', ...)
> -- HANGS with database routers !
>
> class Migration(migrations.Migration):
>     dependencies = [
>         ('myapp', '003_previous_migration'),
>     ]
>
>     operations = [
>         migrations.AddField(
>             model_name='customuser',
>             name='uniq_id',
>             field=models.UUIDField(default=uuid.uuid4, null=True),
>         ),
>         migrations.RunPython(gen_uuid,
> reverse_code=migrations.RunPython.noop),
>         migrations.AlterField(
>             model_name='customuser',
>             name='uniq_id',
>             field=models.UUIDField(default=uuid.uuid4, unique=True),
>         ),
>     ]
> }}}

New description:

 I'm trying to add a UUIDField in an existing user model following this
 method (with unique=True & default=uuid.uuid4).
 https://docs.djangoproject.com/en/1.11/howto/writing-migrations
 /#migrations-that-add-unique-fields

 This works with a single database but hangs in the following scenarios
 with multiple databases :

 - Hangs
   - python manage.py migrate --database=nondefault
   - also hangs with `.using('nondefault')` in the query in gen_uuid
 function

 - Works
   - python manage.py migrate
   - python manage.py migrate --database=default

 It seems to always hang at this statement `UserModel.objects.all()` when a
 non-default database is used either via `--database` option in migrate or
 via `.using('nondefault')` in query.

 Here's a snippet of the code I've used. I would be glad to provide
 additional information to reproduce the issue.

 User model :

 {{{
 class CustomUser(AbstractUser):
     address = models.TextField()
     uniq_id = models.UUIDField(unique=True, default=uuid.uuid4)

     class Meta:
         db_table = 'customuser'
 }}}


 Migration file


 {{{
 def gen_uuid(apps, schema_editor):
     UserModel = apps.get_model('myapp', 'customuser')
     for row in UserModel.objects.all():     #
 .objects.using('foobar').all(): -- HANGS !
         row.uniq_id = uuid.uuid4()
         row.save(update_fields=['uniq_id']) # .save(using='foobar', ...)
 -- HANGS with database routers !

 class Migration(migrations.Migration):
     dependencies = [
         ('myapp', '003_previous_migration'),
     ]

     operations = [
         migrations.AddField(
             model_name='customuser',
             name='uniq_id',
             field=models.UUIDField(default=uuid.uuid4, null=True),
         ),
         migrations.RunPython(gen_uuid,
 reverse_code=migrations.RunPython.noop),
         migrations.AlterField(
             model_name='customuser',
             name='uniq_id',
             field=models.UUIDField(default=uuid.uuid4, unique=True),
         ),
     ]
 }}}

--

-- 
Ticket URL: <https://code.djangoproject.com/ticket/30431#comment:2>
Django <https://code.djangoproject.com/>
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