我更改了模型的 primary_key，现在它的“ForeignKey”模型不起作用

Question

我有一个Post 模型：

class Post(models.Model):
    id = models.CharField(max_length=18, primary_key=True, default=random_string)
    has_upvoted = models.ManyToManyField(User, related_name="has_upvoted")
    has_downvoted = models.ManyToManyField(User, related_name="has_downvoted")

还有一个PostScore 模型：

class PostScore(models.Model):
    user = models.ForeignKey(User, blank=True, null=True)
    post = models.ForeignKey(Post, related_name='score')

因为我最近将我的Post 模型上的id 从默认的id = models.AutoField(primary_key=True) 更改为当前的CharField，所以在我运行migrate 时会导致此错误：

django.db.utils.ProgrammingError: foreign key constraint "post_post_has_downvoted_post_id_3b2ec618_fk_post_post_id" cannot be implemented
DETAIL:  Key columns "post_id" and "id" are of incompatible types: integer and character varying.

知道如何解决这个问题吗？

编辑：

我现在收到了这个IntegrityError - 我不知道为什么，因为我已经删除了与id 的更改相关的所有迁移历史记录，所以它应该会恢复正常。

这是回溯：

Traceback (most recent call last):
  File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/core/management/commands/migrate.py", line 204, in handle
    fake_initial=fake_initial,
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/migrations/executor.py", line 115, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/migrations/executor.py", line 145, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/migrations/executor.py", line 244, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/migrations/migration.py", line 129, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/migrations/operations/fields.py", line 156, in database_forwards
    schema_editor.remove_field(from_model, from_model._meta.get_field(self.name))
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/backends/sqlite3/schema.py", line 256, in remove_field
    self._remake_table(model, delete_field=field)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/backends/sqlite3/schema.py", line 206, in _remake_table
    self.quote_name(model._meta.db_table),
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/backends/base/schema.py", line 120, in execute
    cursor.execute(sql, params)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/Users/zorgan/Desktop/app/lib/python3.5/site-packages/django/db/backends/sqlite3/base.py", line 328, in execute
    return Database.Cursor.execute(self, query, params)
django.db.utils.IntegrityError: datatype mismatch

Answer 1

问题是，当您将 PK 类型从 AutoField 编辑到 CharField 时，它会尝试从旧值获取新类型并失败。如果您想使用 UUID，请尝试改用 UUIDField。

说实话，你应该完全触摸 id 参数。如果您需要将唯一字符串与您的数据库记录相关联，我建议您添加新字段

local_id = models.CharField(unique=True, mac_length=120)

如果你仍然需要你的字符串作为PK，即使不推荐，最简单的方法是删除数据库，这样就不需要将integer转换为varchar。