Django + posgtres 关系不存在错误

Question

我知道这件事有多少问题，但建议的解决方案都没有帮助。我遇到了以下问题：我删除了我的模型并删除了导入admin.py。然后我想更新 django 数据库，makemigrations该数据库显示它删除了模型员工，但在使用migrate命令后，我看到了一个错误，表明该关系不存在。我也从我使用的 postgres 数据库中删除了它。这里奇怪的是 migrate 一直在寻找不存在的模型。即使我创建另一个makemigrations检测到它然后migrate说relation project_employee.. 尝试syncdb --all没有成功。这是输出migrate

Apply all migrations: sessions, project, admin, auth, contenttypes
Running migrations:
Applying project.0003_auto_20160318_1215...Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
psycopg2.ProgrammingError: relation "project_employee" does not exist


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
 File "manage.py", line 10, in <module>
  execute_from_command_line(sys.argv)
File "/usr/lib/python3/dist-packages/django/core/management/__init__.py", line 385, in execute_from_command_line
utility.execute()
File "/usr/lib/python3/dist-packages/django/core/management/__init__.py", line 377, in execute
self.fetch_command(subcommand).run_from_argv(self.argv)
File "/usr/lib/python3/dist-packages/django/core/management/base.py", line 288, in run_from_argv
self.execute(*args, **options.__dict__)
File "/usr/lib/python3/dist-packages/django/core/management/base.py", line 338, in execute
output = self.handle(*args, **options)
File "/usr/lib/python3/dist-packages/django/core/management/commands/migrate.py", line 161, in handle
executor.migrate(targets, plan, fake=options.get("fake", False))
File "/usr/lib/python3/dist-packages/django/db/migrations/executor.py", line 68, in migrate
self.apply_migration(migration, fake=fake)
File "/usr/lib/python3/dist-packages/django/db/migrations/executor.py", line 102, in apply_migration
migration.apply(project_state, schema_editor)
File "/usr/lib/python3/dist-packages/django/db/migrations/migration.py", line 108, in apply
operation.database_forwards(self.app_label, schema_editor, project_state, new_state)
 File "/usr/lib/python3/dist-packages/django/db/migrations/operations/fields.py", line 84, in database_forwards
schema_editor.remove_field(from_model, from_model._meta.get_field_by_name(self.name)[0])
 File "/usr/lib/python3/dist-packages/django/db/backends/schema.py", line 431, in remove_field
self.execute(sql)
 File "/usr/lib/python3/dist-packages/django/db/backends/schema.py", line 111, in execute
cursor.execute(sql, params)
 File "/usr/lib/python3/dist-packages/django/db/backends/utils.py", line 81, in execute
return super(CursorDebugWrapper, self).execute(sql, params)
 File "/usr/lib/python3/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
 File "/usr/lib/python3/dist-packages/django/db/utils.py", line 94, in __exit__
six.reraise(dj_exc_type, dj_exc_value, traceback)
 File "/usr/lib/python3/dist-packages/django/utils/six.py", line 658, in reraise
raise value.with_traceback(tb)
 File "/usr/lib/python3/dist-packages/django/db/backends/utils.py", line 65, in execute
return self.cursor.execute(sql, params)
 django.db.utils.ProgrammingError: relation "project_employee" does not exist

`

谢谢

Answer 1

AFAIK，您不应该在迁移之前直接从数据库中删除表。如果你改变你的模型，那么manage.py migrate就会做这件事。

django无法检测到DB的直接变化；只知道模型脚本的变化。因此，如果你删除一个表，那么 django 不会检测到更改，因此 django 会继续查找被删除的表并给出错误。

有时迁移会无缘无故地不起作用。在这种情况下，我会做以下事情：

1. 撤消 models.py 的更改
2. 进行 django 迁移（manage.py makemigrations appname效果比 更好manage.py makemigrations）
3. 如果迁移有效，则再次更改 models.py
4. 再次进行 django 迁移

这有时有效。

Answer 2

我能够通过以下步骤解决这个问题

1. 当我运行这个命令时

   python manage.py migrate app_name zero

   它抱怨缺少一些桌子。所以我创建了一个带有虚拟列的虚拟表。

2. 我再次运行命令

   python manage.py migrate app_name zero

3. 我已经为该应用程序应用了迁移

   python manage.py migrate app_name

Answer 3

最终有帮助的是从项目文件夹中删除整个迁移文件夹。也看到了一些南方的回复，但没有尝试过。