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maininformer
maininformer

Reputation: 1077

Django : Duplicate entry in uuid4

I added a new uuid field to my table, user_table, with existing rows. Due to a race condition I am getting the "Duplicate entry" error when migrating. I then followed the steps here:

http://django.readthedocs.org/en/latest/howto/writing-migrations.html

Now my first and second migrations run but my last migrations gives me the same error. My 3 migrations per the link are as follows:

Migration '0009_label'

from __future__ import unicode_literals

from django.db import models, migrations
import uuid


class Migration(migrations.Migration):

    dependencies = [
        ('app', '0008_label'),
    ]

    operations = [
        migrations.AddField(
            model_name='user_table',
            name='UUID_loc',
            field=models.UUIDField(default=uuid.uuid4, null=True),
        ),
        migrations.AlterField(
            model_name='another_table',
            name='Time',
            field=models.CharField(default=0, max_length=3),
        ),
    ]

Migration '0010_label'

from __future__ import unicode_literals

from django.db import migrations, models
import uuid

def gen_uuid(apps, schema_editor):
    MyModel = apps.get_model('app', 'user_table')
    for row in MyModel.objects.all():
        row.uuid = uuid.uuid4()
        row.save()

class Migration(migrations.Migration):

    dependencies = [
        ('app', '0009_label'),
    ]

    operations = [
        # omit reverse_code=... if you don't want the migration to be reversible.
        migrations.RunPython(gen_uuid, reverse_code=migrations.RunPython.noop),
    ]

Migration '0011_label'

from __future__ import unicode_literals

from django.db import models, migrations
import uuid


class Migration(migrations.Migration):

    dependencies = [
        ('app', '0010_label'),
    ]

    operations = [
        migrations.AlterField(
            model_name='user_table',
            name='UUID_loc',
            field=models.UUIDField(default=uuid.uuid4, unique=True),
        ),

    ]

The link was very relevant to me but unfortunately I am getting the same error. Now I am stuck here where my tables have the UUID_loc field, but it is not unique yet, i.e. the third migration isn't run yet. Can anyone please provide some insight? Thank you.

Upvotes: 3

Views: 2320

Answers (1)

Nick
Nick

Reputation: 1194

I think you should to slightly edit your second migration to prevent django from updating your models with duplicate uuid values. 

def gen_uuid(apps, schema_editor):
    MyModel = apps.get_model('app', 'user_table')
    for row in MyModel.objects.all():
        while True:
            row.uuid = uuid.uuid4()
            if not MyModel.objects.filter(uuid=row.uuid).exists():
                break

        row.save()

The you should re-run your second migration again and then you should be able to run third migration without any problems.

Upvotes: 3

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