sql – django.db.utils.IntegrityError：列“venue_city”包含空值

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.

这一切都是在我将模型从CharField更改为ForeignKey时开始的.
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'),),]

解决方法

看起来您在创建迁移文件后添加了null = True.因为venue_city不是迁移文件中的可空字段

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