django.db.utils.IntegrityError:列"venue_city"包含空值

Question

我已经在stackoverflow和google上阅读了很多其他帖子,但我找不到解决方案.

当我将模型从CharField更改为ForeignKey时,一切都开始了.我收到的错误是:

Operations to perform:
  Synchronize unmigrated apps: gis, staticfiles, crispy_forms, geoposition, messages
  Apply all migrations: venues, images, amenities, cities_light, registration, auth, admin, sites, sessions, contenttypes, easy_thumbnails, newsletter
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states... DONE
  Applying venues.0016_auto_20160514_2141...Traceback (most recent call last):
  File "/Users/iam-tony/.envs/venuepark/lib/python3.4/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
psycopg2.IntegrityError: column "venue_city" contains null values

我的模型如下:

class Venue(models.Model):
    venue_city = models.ForeignKey(City, null=True,)
    venue_country=models.ForeignKey(Country, null=True)

之前不存在venue_country,因此迁移成功.但是venue_city是CharField.

我对迁移文件进行了一些更改,以便它按如下方式执行sql:

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('venues', '0011_venue_map_activation'),
    ]

    migrations.RunSQL(''' ALTER TABLE venues_venue ALTER venue_city TYPE integer USING  venue_city::integer '''),

    migrations.RunSQL(''' ALTER TABLE venues_venue ALTER venue_city RENAME COLUMN venue_city TO venue_city_id '''),

    migrations.RunSQL(''' ALTER TABLE venues_venue ADD CONSTRAINT venues_venus_somefk FOREIGN KEY (venue_city_id) REFERENCES  cities_light (id) DEFERRABLE INITIALLY DEFERRED'''),

提前致谢!

更新:我的新迁移文件:

# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('cities_light', '0006_compensate_for_0003_bytestring_bug'),
        ('venues', '0024_remove_venue_venue_city'),
    ]

    operations = [
        migrations.AddField(
            model_name='venue',
            name='venue_city',
            field=models.ForeignKey(null=True, to='cities_light.City'),
        ),
    ]

Answer 1

看起来您null=True在创建迁移文件后添加了.因为venue_city迁移文件中不是可为空的字段

跟着这些步骤.

1) Drop venue_city & venue_country from your local table
3) Delete all the migration files you created for these `CharField to a ForeignKey` change
4) execute `python manage.py makemigrations`
5) execute 'python manage.py migrate'

它应该工作

Answer 2

有一个类似的问题，我通过删除以前的迁移文件解决了它。没有技术解释

Answer 3

我通过添加null = True到导致问题的（自动生成的）迁移文件和模型中来解决它。然后migrate，您失败的迁移现在将成功。由于您也在模型中更改了它，因此makemigration之后将检测不到任何更改。