Django manage.py 迁移验证错误

Question

当我使用python manage.py migrate运行 django 时，我在运行python manage.py makemigrations后遇到以下错误

File "manage.py", line 22, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
    utility.execute()
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/core/management/__init__.py", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/core/management/base.py", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/core/management/base.py", line 364, in execute
    output = self.handle(*args, **options)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/core/management/base.py", line 83, in wrapped
    res = handle_func(*args, **kwargs)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/core/management/commands/migrate.py", line 234, in handle
    fake_initial=fake_initial,
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/migrations/executor.py", line 117, in migrate
    state = self._migrate_all_forwards(state, plan, full_plan, fake=fake, fake_initial=fake_initial)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/migrations/executor.py", line 147, in _migrate_all_forwards
    state = self.apply_migration(state, migration, fake=fake, fake_initial=fake_initial)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/migrations/executor.py", line 245, in apply_migration
    state = migration.apply(state, schema_editor)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/migrations/migration.py", line 124, in apply
    operation.database_forwards(self.app_label, schema_editor, old_state, project_state)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/migrations/operations/fields.py", line 112, in database_forwards
    field,
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 433, in add_field
    definition, params = self.column_sql(model, field, include_default=True)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 161, in column_sql
    default_value = self.effective_default(field)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/backends/base/schema.py", line 233, in effective_default
    return field.get_db_prep_save(self._effective_default(field), self.connection)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/models/fields/__init__.py", line 789, in get_db_prep_save
    return self.get_db_prep_value(value, connection=connection, prepared=False)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/models/fields/__init__.py", line 1429, in get_db_prep_value
    value = self.get_prep_value(value)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/models/fields/__init__.py", line 1408, in get_prep_value
    value = super().get_prep_value(value)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/models/fields/__init__.py", line 1268, in get_prep_value
    return self.to_python(value)
  File "/Users/rasikraj/Desktop/eb-virt/lib/python3.7/site-packages/django/db/models/fields/__init__.py", line 1393, in to_python
    params={'value': value},
django.core.exceptions.ValidationError: ["'' value has an invalid format. It must be in YYYY-MM-DD HH:MM[:ss[.uuuuuu]][TZ] format."]

此错误的原因可能是什么以及如何解决此问题。 我正在使用 python 3.7 和 Django 2.2

Answer 1

根据错误，有一个DateTimeField [Django-doc] with as default='' [Django-doc] 。 但这不是一个有效的默认值： DateTimeField应该在数据库中存储一个日期时间（或者None以防该字段为NULL ）。

因此，您应该为该DateTimeField提供一个有效的默认值，例如：

from django.utils import timezone

class SomeModel(models.Model):
    my_field = DateTimeField(default=timezone.now)

或者您可以省略默认值，并运行makemigrations 。 在这种情况下，Django 会询问您是否要提供一次性默认值，该默认值将应用于数据库中已有的记录。

更改字段后，您需要删除在添加（或更改）该字段时构建的（无效）迁移文件，并使用manage.py makemigrations进行新迁移。 毕竟，在构建迁移文件时不会发生这种验证，现在您迁移它确实会出错。 如果稍后更改模型，仍然不会执行无效的迁移填充，因此它会再次引发相同的错误。