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我收到的時候我嘗試運行Django的遷移命令「關係的列已經存在」錯誤：修復'列已經存在'Django遷移錯誤？
Operations to perform:
Synchronize unmigrated apps: signin, django_rq, gis, staticfiles, admindocs, messages, pipeline, test_without_migrations, django_extensions
Apply all migrations: profile, activities, contenttypes, # plus other modules...
Synchronizing apps without migrations:
Creating tables...
Running deferred SQL...
Installing custom SQL...
Running migrations:
Rendering model states... DONE
Applying activities.0002_auto_20170731_1939...Traceback (most recent call last):
File "manage.py", line 10, in <module>
execute_from_command_line(sys.argv)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
utility.execute()
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/core/management/__init__.py", line 330, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/core/management/base.py", line 393, in run_from_argv
self.execute(*args, **cmd_options)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/core/management/base.py", line 444, in execute
output = self.handle(*args, **options)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/core/management/commands/migrate.py", line 222, in handle
executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 110, in migrate
self.apply_migration(states[migration], migration, fake=fake, fake_initial=fake_initial)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/migrations/executor.py", line 148, in apply_migration
state = migration.apply(state, schema_editor)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/migrations/migration.py", line 115, in apply
operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/migrations/operations/fields.py", line 62, in database_forwards
field,
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/contrib/gis/db/backends/postgis/schema.py", line 94, in add_field
super(PostGISSchemaEditor, self).add_field(model, field)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 398, in add_field
self.execute(sql, params)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/backends/base/schema.py", line 111, in execute
cursor.execute(sql, params)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 79, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/utils.py", line 97, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
File "/srv/http/example.com/venvs/4dc40e5fc12700640a30ae0f040aa07ffc8aa1c5/local/lib/python2.7/site-packages/django/db/backends/utils.py", line 64, in execute
return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: column "country_id" of relation "travel" already exists
的旅遊類從活動類繼承：
# activities/models.py
from profile.models import Country
class Activity(models.Model):
host = models.ForeignKey(User)
# other fields...
class Meta:
abstract = True
class Travel(Activity):
start_date = models.DateField()
country = models.ForeignKey(Country)
# other fields...
國家由外鍵引用的類位於另一個模塊中。它本質上是一個查找表將包含每個國家代碼（簡稱）和 名稱：
# profile/models.py
class Country(models.Model):
country_cd = models.CharField(max_length=2)
descrip = models.CharField(max_length=50)
我看不出有什麼出格的遷移普通的文件不是事實，其他的有兩種遷移活動文件（我不太明白）：
# activities/migrations/0001_initial.py
class Migration(migrations.Migration):
dependencies = [
]
operations = [
migrations.CreateModel(
name='Travel',
fields=[
('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
('name', models.CharField(max_length=256)),
# other fields but none that reference Country
],
options={
'db_table': 'travel',
},
),
]
# activities/migrations/0002_auto_20170731_1939.py
class Migration(migrations.Migration):
dependencies = [
migrations.swappable_dependency(settings.AUTH_USER_MODEL),
('profile', '0001_initial'),
('activities', '0001_initial'),
]
operations = [
migrations.AddField(
model_name='travel',
name='country',
field=models.ForeignKey(to='profile.Country'),
),
migrations.AddField(
model_name='travel',
name='host',
field=models.ForeignKey(to=settings.AUTH_USER_MODEL),
),
# other fields...
]
我不明白爲什麼我得到這個錯誤。我注意到在聲明外鍵關係的其他模型中我沒有這個問題。但是，在所有這些模型中，外鍵關係都是auth.models.User或同一模型文件中的另一個類。我最近閱讀了一篇文章Tips for Building High-Quality Django Apps at Scale，其中作者說如果您有跨應用程序外鍵，則可能會遇到遷移問題，所以問題可能與此有關。我可以在活動模塊內重新創建'Country'類，但這不會幹。我不知道如何解決這個問題。
您是否爲現有數據庫創建了遷移，或者您剛啓動了此項目？ – Alasdair
這是對現有數據庫的遷移。遷移曾經運行，但現在他們沒有。奇怪的是，我有一段時間沒有改變相關的活動模型。 – William