(Django Migration Bug with PostgreSQL) django.db.utils.ProgrammingError: 关系“subjects_subject”不存在答案

【问题标题】：(Django Migration Bug with PostgreSQL) django.db.utils.ProgrammingError: relation "subjects_subject" does not exist(Django Migration Bug with PostgreSQL) django.db.utils.ProgrammingError: 关系“subjects_subject”不存在
【发布时间】：2021-04-07 12:40:57
【问题描述】：

**链接 github 到这个 repo : **https://github.com/thetruefuss/elmer

当我使用sqlite作为数据库启动这个项目时，它完美地与数据库一起迁移，但是当我将它切换到POSTGRESQL时，它得到了这个错误：

django.db.utils.ProgrammingError: relation "subjects_subject" does not exist
LINE 1: ...ect"."created", "subjects_subject"."updated" FROM "subjects_...

要点是：在这个 repo 中它已经拥有所有模型的所有迁移文件，你可以签入这个 repo，我不能在 pgadmin 4 中使用数据库迁移它

db settings.py

    DATABASES = {
      'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'demo_postgres',
        'USER':'postgres',
        'PASSWORD':'18092000',
        'PORT':'5432',
        'HOST':'127.0.0.1',
      }
    }

** 我的命令 **

python manage.py migrate

subjects_subject（迁移文件）


    class Migration(migrations.Migration):

    initial = True

    dependencies = [
        migrations.swappable_dependency(settings.AUTH_USER_MODEL),
        ('boards', '0001_initial'),
    ]

    operations = [
        migrations.CreateModel(
            name='Subject',
            fields=[
                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
                ('title', models.CharField(db_index=True, max_length=150)),
                ('slug', models.SlugField(blank=True, max_length=150, null=True)),
                ('body', models.TextField(blank=True, max_length=5000, null=True)),
                ('photo', models.ImageField(blank=True, null=True, upload_to='subject_photos/', verbose_name='Add image (optional)')),
                ('rank_score', models.FloatField(default=0.0)),
                ('active', models.BooleanField(default=True)),
                ('created', models.DateTimeField(default=django.utils.timezone.now)),
                ('updated', models.DateTimeField(auto_now=True)),
                ('author', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='posted_subjects', to=settings.AUTH_USER_MODEL)),
                ('board', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, related_name='submitted_subjects', to='boards.Board')),
                ('mentioned', models.ManyToManyField(blank=True, related_name='m_in_subjects', to=settings.AUTH_USER_MODEL)),
                ('points', models.ManyToManyField(blank=True, related_name='liked_subjects', to=settings.AUTH_USER_MODEL)),
            ],
            options={
                'ordering': ('-created',),
            },
        ),
    ]

subjects_subject(model_file)

    class Subject(models.Model):
    """
    Model that represents a subject.
    """
    title = models.CharField(max_length=150, db_index=True)
    slug = models.SlugField(max_length=150, null=True, blank=True)
    body = models.TextField(max_length=5000, blank=True, null=True)
    photo = models.ImageField(
        upload_to='subject_photos/', verbose_name=u"Add image (optional)",
        blank=True, null=True
    )
    author = models.ForeignKey(User, related_name='posted_subjects', on_delete=models.CASCADE)
    board = models.ForeignKey(Board, related_name='submitted_subjects', on_delete=models.CASCADE)
    points = models.ManyToManyField(
        settings.AUTH_USER_MODEL, related_name='liked_subjects', blank=True
    )
    mentioned = models.ManyToManyField(
        User, related_name='m_in_subjects', blank=True
    )
    rank_score = models.FloatField(default=0.0)
    active = models.BooleanField(default=True)
    created = models.DateTimeField(default=timezone.now)
    updated = models.DateTimeField(auto_now=True)

    class Meta:
        ordering = ('-created',)

编辑：1（完整追溯）

 File "E:\Python\elmer\manage.py", line 15, in <module>
   execute_from_command_line(sys.argv)
 File "E:\Python\elmer\venv\lib\site-packages\django\core\management\__init__.py", line 381, in execute_from_command_line
   utility.execute()
 File "E:\Python\elmer\venv\lib\site-packages\django\core\management\__init__.py", line 375, in execute
   self.fetch_command(subcommand).run_from_argv(self.argv)
 File "E:\Python\elmer\venv\lib\site-packages\django\core\management\base.py", line 316, in run_from_argv
   self.execute(*args, **cmd_options)
 File "E:\Python\elmer\venv\lib\site-packages\django\core\management\base.py", line 350, in execute
   self.check()
 File "E:\Python\elmer\venv\lib\site-packages\django\core\management\base.py", line 376, in check
   all_issues = self._run_checks(
 File "E:\Python\elmer\venv\lib\site-packages\django\core\management\commands\migrate.py", line 60, in _run_checks
   issues.extend(super()._run_checks(**kwargs))
 File "E:\Python\elmer\venv\lib\site-packages\django\core\management\base.py", line 366, in _run_checks
   return checks.run_checks(**kwargs)
 File "E:\Python\elmer\venv\lib\site-packages\django\core\checks\registry.py", line 71, in run_checks
   new_errors = check(app_configs=app_configs)
 File "E:\Python\elmer\venv\lib\site-packages\django\core\checks\urls.py", line 13, in check_url_config
   return check_resolver(resolver)
 File "E:\Python\elmer\venv\lib\site-packages\django\core\checks\urls.py", line 23, in check_resolver
   return check_method()
 File "E:\Python\elmer\venv\lib\site-packages\django\urls\resolvers.py", line 396, in check
   for pattern in self.url_patterns:
 File "E:\Python\elmer\venv\lib\site-packages\django\utils\functional.py", line 37, in __get__
   res = instance.__dict__[self.name] = self.func(instance)
 File "E:\Python\elmer\venv\lib\site-packages\django\urls\resolvers.py", line 533, in url_patterns
   patterns = getattr(self.urlconf_module, "urlpatterns", self.urlconf_module)
 File "E:\Python\elmer\venv\lib\site-packages\django\utils\functional.py", line 37, in __get__
   res = instance.__dict__[self.name] = self.func(instance)
 File "E:\Python\elmer\venv\lib\site-packages\django\urls\resolvers.py", line 526, in urlconf_module
   return import_module(self.urlconf_name)
 File "C:\Program Files\WindowsApps\PythonSoftwareFoundation.Python.3.9_3.9.496.0_x64__qbz5n2kfra8p0\lib\importlib\__init__.py", line 127, in import_module
   return _bootstrap._gcd_import(name[level:], package, level)
 File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
 File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
 File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
 File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
 File "<frozen importlib._bootstrap_external>", line 790, in exec_module
 File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
 File "E:\Python\elmer\mysite\urls.py", line 33, in <module>
   import subjects.views as subjects_views
 File "E:\Python\elmer\subjects\views.py", line 58, in <module>
   class TrendingPageView(ListView):
 File "E:\Python\elmer\subjects\views.py", line 63, in TrendingPageView
   queryset = get_trending_subjects()
 File "E:\Python\elmer\subjects\views.py", line 25, in get_trending_subjects
   for subject in subjects:
 File "E:\Python\elmer\venv\lib\site-packages\django\db\models\query.py", line 268, in __iter__
   self._fetch_all()
 File "E:\Python\elmer\venv\lib\site-packages\django\db\models\query.py", line 1186, in _fetch_all
   self._result_cache = list(self._iterable_class(self))
 File "E:\Python\elmer\venv\lib\site-packages\django\db\models\query.py", line 54, in __iter__
   results = compiler.execute_sql(chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size)
 File "E:\Python\elmer\venv\lib\site-packages\django\db\models\sql\compiler.py", line 1065, in execute_sql
   cursor.execute(sql, params)
 File "E:\Python\elmer\venv\lib\site-packages\django\db\backends\utils.py", line 100, in execute
   return super().execute(sql, params)
 File "E:\Python\elmer\venv\lib\site-packages\django\db\backends\utils.py", line 68, in execute
   return self._execute_with_wrappers(sql, params, many=False, executor=self._execute)
 File "E:\Python\elmer\venv\lib\site-packages\django\db\backends\utils.py", line 77, in _execute_with_wrappers
   return executor(sql, params, many, context)
 File "E:\Python\elmer\venv\lib\site-packages\django\db\backends\utils.py", line 85, in _execute
   return self.cursor.execute(sql, params)
 File "E:\Python\elmer\venv\lib\site-packages\django\db\utils.py", line 89, in __exit__
   raise dj_exc_value.with_traceback(traceback) from exc_value
 File "E:\Python\elmer\venv\lib\site-packages\django\db\backends\utils.py", line 85, in _execute
   return self.cursor.execute(sql, params)
django.db.utils.ProgrammingError: relation "subjects_subject" does not exist
LINE 1: ...ect"."created", "subjects_subject"."updated" FROM "subjects_...
                                                            ^

【问题讨论】：

这个错误究竟是在哪里引发的？您能否包含完整的回溯。这似乎是一个读取/查询，这可能意味着您的迁移乱序，或者您在应用启动时执行了一些查询
谢谢先生，我已经在编辑中添加了回溯

标签： django postgresql migration relation migrate

【解决方案1】：

您的问题是您在应用程序启动时执行数据库查询，这会导致迁移出现很多问题，通常不鼓励。

在TrendingPageView 类的主体中，您正在调用get_trending_subjects()，它正在对Subject 模型执行查询，您需要将其移动到一个方法中，以便在启动时不调用它，但当视图被访问。

class TrendingPageView(ListView):
    model = Subject
    paginate_by = 15
    template_name = 'subjects/trending.html'
    context_object_name = 'subjects'

    def get_queryset(self):
        return get_trending_subjects()

【讨论】：

哦，先生，我解决了我的问题，但是： 1. 为什么在课堂上HomePageView(ListView) 我打电话给queryset = get_home_subjects() 但它不会导致错误？？ 2. 为什么当我使用 sqlite 3 db 运行时，它没有导致错误，但 postgres 会？这是因为它们不同吗？或者什么class HomePageView(ListView): model = Subject queryset = get_home_subjects() paginate_by = 15 template_name = 'subjects/home.html' context_object_name = 'subjects'
get_home_subjects() 调用Subject.get_subjects() 并返回一个查询集但不执行它。只有当您迭代执行它的查询集时，在get_trending_subjects() 中您迭代查询集 (for subject in subjects:) 并导致它被执行。至于 sqlite vs postgres 的事情，我假设你已经在你的 sqlite DB 中有表并且不在 postgres 中？
我明白了，谢谢先生，您解决了我的问题，非常感谢，非常感谢