Django数据库迁移与Postgres失败。

Question

我对我的模型进行了一些更改，然后运行了以下命令：

python manage.py makemigrations python manage.py migrate

但是我收到了这个回溯：

Operations to perform:
  Synchronize unmigrated apps: staticfiles, messages
  Apply all migrations: sessions, admin, study, auth, quiz, contenttypes, main
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states... DONE
  Applying quiz.0013_auto_20151005_0644...Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 330, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 393, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 444, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 222, in handle
    executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 110, in migrate
    self.apply_migration(states[migration], migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 154, in apply_migration
    self.recorder.record_applied(migration.app_label, migration.name)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/recorder.py", line 67, in record_applied
    self.migration_qs.create(app=app, name=name)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 348, in create
    obj.save(force_insert=True, using=self.db)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 734, in save
    force_update=force_update, update_fields=update_fields)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 762, in save_base
    updated = self._save_table(raw, cls, force_insert, force_update, using, update_fields)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 846, in _save_table
    result = self._do_insert(cls._base_manager, using, fields, update_pk, raw)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/base.py", line 885, in _do_insert
    using=using, raw=raw)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/manager.py", line 127, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/query.py", line 920, in _insert
    return query.get_compiler(using=using).execute_sql(return_id)
  File "/usr/local/lib/python2.7/dist-packages/django/db/models/sql/compiler.py", line 974, in execute_sql
    cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 97, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
django.db.utils.IntegrityError: duplicate key value violates unique constraint "django_migrations_pkey"
DETAIL:  Key (id)=(27) already exists.

我不太清楚如何解释主键已经存在的错误。但很奇怪的是，它仍将该字段添加到数据库中，因为我在网站上看到了输出，并且当我运行 shell 时，我可以看到字段已添加且填充了我的默认数据。

我决定再次运行迁移以查看第二次是否能通过，结果出现了不同的回溯信息...

   Operations to perform:
  Synchronize unmigrated apps: staticfiles, messages
  Apply all migrations: sessions, admin, study, auth, quiz, contenttypes, main
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states... DONE
  Applying quiz.0013_auto_20151005_0644...Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/__init__.py", line 330, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 393, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/base.py", line 444, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python2.7/dist-packages/django/core/management/commands/migrate.py", line 222, in handle
    executor.migrate(targets, plan, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 110, in migrate
    self.apply_migration(states[migration], migration, fake=fake, fake_initial=fake_initial)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/executor.py", line 148, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/migration.py", line 115, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/usr/local/lib/python2.7/dist-packages/django/db/migrations/operations/fields.py", line 62, in database_forwards
    field,
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/schema.py", line 398, in add_field
    self.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/base/schema.py", line 111, in execute
    cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/usr/local/lib/python2.7/dist-packages/django/db/utils.py", line 97, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/usr/local/lib/python2.7/dist-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: column "lang1_back_to_choice" of relation "quiz_langpairinstructions" already exists

现在，如果我再试一次，我将总是得到第二个回溯。 我想知道我应该怎么做才能在未来进行迁移。 如果在数据库本身中一切都顺利，为什么我会收到此错误？

- Joff

Answer 1

还有一种方法。由于您知道django_migrations表中的最后一个id值，假设它是100。那么，您需要执行以下操作：

ALTER SEQUENCE django_migrations_id_seq RESTART WITH 101;

- Anatoly Scherbakov

Answer 2

我忽略了'django_migrations_pkey'列的名称，并没有意识到它在数据库中存在。某种程度上，Django比实际数据库慢一步，并尝试使用主键（pk = 27）而不是实际上应该有的数字（应该是28）。

我不确定如何在Django内部更改此设置，因此我只是从数据库中删除了最后一列，使其少了一个主键，与Django保持一致，然后它开始正常工作了。

- Joff

---

您能否提供您用于删除最后一列的命令以及应该删除哪个表格？这将使您的答案对像我这样的新开发人员非常有用。 - Khay

Answer 3

在我手动修改django migrations表项之后（在添加了一些有问题的迁移操作后又删除了它们），我遇到了这个错误。

这导致django_migrations中的ID顺序（就这么说吧）与django_migrations表中条目的默认位置不一致。

问题在于，django获取最后一项的ID并加1来创建新条目（在下面的表格中：197 + 1 = 198），但是如您所见，键（id）=（198）已经存在于该表中。

187 | foo_app             | 0016_auto_20161220_2332                     | 2017-01-06 05:22:07.666172+00
198 | bar_app             | 0004_auto_20160423_2122                     | 2017-01-13 05:38:31.922738+00
197 | baz_app             | 0013_auto_20170203_2311                     | 2017-02-08 18:50:22.70143+00

如您所见，左侧的主键数字是无序的。 我的做法是手动删除django_migration中无序条目，然后重新添加。

DELETE from django_migrations where name = '0004_auto_20160423_2122';
DELETE from django_migrations where name = '0013_auto_20170203_2311';

INSERT INTO django_migrations VALUES (188, 'baz_app', '0013_auto_20170203_2311', date());
INSERT INTO django_migrations VALUES (189, 'bar_app', '0004_auto_20160423_2122', date());

需要注意的是，我最初尝试添加“new_app”，并对其进行迁移，“0002_auto_00000000_1111”实际上修改了Postgres中的“new_app”表，但是“django_migrations”表没有得到更新。

因此，第二次尝试重新运行迁移“0002_auto_00000000_1111”时，出现了错误：

django.db.utils.ProgrammingError: column "new_app_field" of relation "new_app_new" already exists

我上面提供的解决方案解决了我的问题。

- lukeaus

Answer 4

对我来说，简单重建django_migrations表就可以解决问题。

请按照以下步骤在您的终端中操作：

切换用户为root

$ sudo su

这样你就可以将用户更改为postgres

$ su postgres

打开PostgreSQL终端客户端，并选择您的数据库

$ psql name_of_your_db

在Postgres客户端中，输入以下命令。

REINDEX TABLE django_migrations;

然后退出Postgres客户端

\q

- PhoebeB

---

在我的数据库 GUI 中，我选择了重新索引的选项，这是一个指向 PostgreSQL 文档的链接：https://www.postgresql.org/docs/9.3/sql-reindex.html - PhoebeB