loaddata 在迁移中调用时引发 IntegrityError，但如果从 CLI 调用则有效

Question

对于我的 Django 1.8.12 站点，我有一个 example_content 固定装置，用于填充一些初始站点内容。

如果我在运行ning migrate 之后立即加载它，它可以正常导入：

$ ./manage.py migrate --noinput
Operations to perform:
  Synchronize unmigrated apps: ckeditor, staticfiles, zinnia_ckeditor, messages, djangocms_admin_style, webapp_creator, template_debug, sekizai, django_pygments, treebeard
  Apply all migrations: djangocms_inherit, djangocms_snippet, api_docs, cmsplugin_zinnia, sites, menus, contenttypes, store_data, zinnia, django_comments, sessions, rev
ersion, auth, djangocms_picture, tagging, developer_portal, admin, djangocms_link, djangocms_video, django_openid_auth, md_importer, cms, djangocms_text_ckeditor
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states... DONE
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  ... (skipped for brevity).
  Applying django_comments.0003_add_submit_date_index... OK
$ ./manage.py loaddata example_content
Installed 139582 object(s) from 1 fixture(s)
$

但是，我希望这些数据在 migrate 上自动导入，而不是需要额外的手动 loaddata 步骤，所以我正在尝试创建一个迁移，my_app.0002_example_content, 调用 loaddata 命令。

我通过在每个相关模块上添加依赖项来确保首先加载所有其他数据。

为了确认此迁移确实是运行最后一次（就像上面成功时一样），我首先注释掉了 RunPython 步骤，将迁移留空：

# my_app/migrations/0002_example_content.py

from django.core.management import call_command
from django.db import models, migrations

class Migration(migrations.Migration):
    from django.core.management import call_command
    from django.db import models, migrations

    dependencies = [
        ('djangocms_inherit', '0002_auto_20150622_1244'),
        ... all other apps (skipped for brevity)
        ('my_app', '0001_initial'),
    ]
    operations = [
#        migrations.RunPython(
#            lambda apps, schema_editor: call_command("loaddata", "example_content")
#        )
    ]

果然运行是最后一次迁移：

$ ./manage.py migrate --noinput
Operations to perform:
  Synchronize unmigrated apps: ckeditor, staticfiles, zinnia_ckeditor, messages, djangocms_admin_style, webapp_creator, template_debug, sekizai, django_pygments, treebeard
  Apply all migrations: djangocms_inherit, djangocms_snippet, api_docs, cmsplugin_zinnia, sites, menus, contenttypes, store_data, zinnia, django_comments, sessions, reversion, auth, djangocms_picture, tagging, developer_portal, admin, djangocms_link, djangocms_video, django_openid_auth, md_importer, cms, djangocms_text_ckeditor
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states... DONE
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  ... (skipped for brevity)
  Applying django_comments.0003_add_submit_date_index... OK
  Applying my_app.0001_initial... OK
  Applying my_app.0002_example_content... OK
$

然而，当我尝试运行它实际上运行 loaddata 命令（重新注释代码）时，我得到一个错误：

$ ./manage.py migrate --noinput
Operations to perform:
  Synchronize unmigrated apps: ckeditor, staticfiles, zinnia_ckeditor, messages, djangocms_admin_style, webapp_creator, template_debug, sekizai, django_pygments, treebeard
  Apply all migrations: djangocms_inherit, djangocms_snippet, api_docs, cmsplugin_zinnia, sites, menus, contenttypes, store_data, zinnia, django_comments, sessions, reversion, auth, djangocms_picture, tagging, developer_portal, admin, djangocms_link, djangocms_video, django_openid_auth, md_importer, cms, djangocms_text_ckeditor
Synchronizing apps without migrations:
  Creating tables...
    Running deferred SQL...
  Installing custom SQL...
Running migrations:
  Rendering model states... DONE
  Applying contenttypes.0001_initial... OK
  Applying auth.0001_initial... OK
  Applying admin.0001_initial... OK
  ... (skipped for brevity)
  Applying django_comments.0003_add_submit_date_index... OK
  Applying my_app.0001_initial... OK
  Applying my_app.0002_example_content...Traceback (most recent call last):
...
django.db.utils.IntegrityError: Problem installing fixtures: The row in table 'django_comments' with primary key '1' has an invalid foreign key: django_comments.content
_type_id contains a value '37' that does not have a corresponding value in django_content_type.id.

鉴于我的新迁移肯定是运行之后的一切，顺序应该与我手动调用 loaddata 时的顺序完全相同。所以我不明白为什么它在通过 CLI 调用时会成功，但在通过迁移调用时会失败。

在 migrate 步骤结束时是否发生了我遗漏的事情，这可能解释了这里的差异？

Answer 1

Django 使用 post_migrate 信号来创建缺失的内容类型，因此如果这是您第一次在当前数据库上迁移，则内容类型将不存在，直到加载数据的迁移具有运行.

您可以手动创建迁移中需要的内容类型。 Django 将检测现有的内容类型，并且不会创建任何重复项。

请注意，内容类型的特定 ID 可能因数据库而异。使用 natural foreign keys 转储数据可能更好。

Answer 2

在的提示下，我设法解决了这个问题。

最初我尝试手动调用 update_contenttypes, but that on its own didn't work. It turns out I need to actually call all the post_migrate 信号，因为我猜他们会做更多需要的整理工作。

这是我最后得到的my_app.0002_example_content：

# my_app/migrations/0002_example_content.py

from django.core.management import call_command
from django.db import migrations
from django.apps import apps
from django.db.models.signals import post_migrate


def finish_previous_migrations(migrate_apps):
    """
    Explicitly run the post_migrate actions
    for all apps
    """

    for app_config in apps.get_app_configs():
        post_migrate.send(
            sender=app_config,
            app_config=app_config
        )


def load_site_content(migrate_apps, schema_editor):
    """
    Load the website content fixture
    """

    finish_previous_migrations(migrate_apps)

    call_command("loaddata", "example_content")


class Migration(migrations.Migration):
    dependencies = [
        ('djangocms_inherit', '0002_auto_20150622_1244'),
        ... all other apps (skipped for brevity)
        ('my_app', '0001_initial'),
    ]
    operations = [
        migrations.RunPython(load_site_content)
    ]

loaddata 在迁移中调用时引发 IntegrityError，但如果从 CLI 调用则有效

loaddata raises IntegrityError when called within migration, but works if called from the CLI

django

loaddata

django-manage.py

django-fixtures

django-migrations