Django“MigrationSchemaMissing：无法创建 django_migrations 表（未选择要创建的模式）”

Question

我正在尝试将生产数据库恢复到我的本地计算机，类似于为 Heroku (https://devcenter.heroku.com/articles/heroku-postgres-import-export) 描述的工作流程。但是，我使用的是 Aptible，它为此提供了 DB tunnel。

使用 pgAdmin4，我创建了一个“自定义”备份。然后，稍微修改了一个 pgAdmin 命令，我使用

恢复了它

"/Applications/pgAdmin 4.app/Contents/SharedSupport/pg_restore" --host "localhost" --port "5432" --username "postgres" --no-password --dbname "lucy_prod" --verbose "/Users/kurtpeek/lucy-prod-backup-11-june-2018" --clean

我在其中添加了--clean 选项以在重新创建数据库对象之前删除它们（参见https://www.postgresql.org/docs/9.2/static/app-pgrestore.html）。

问题是当我现在尝试python manage.py migrate 时，我收到以下错误：

(venv) Kurts-MacBook-Pro-2:lucy-web kurtpeek$ python manage.py migrate
Traceback (most recent call last):
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 62, in execute
    return self.cursor.execute(sql)
psycopg2.ProgrammingError: no schema has been selected to create in
LINE 1: CREATE TABLE "django_migrations" ("id" serial NOT NULL PRIMA...
                     ^


The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/migrations/recorder.py", line 57, in ensure_schema
    editor.create_model(self.Migration)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 303, in create_model
    self.execute(sql, params or None)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/backends/base/schema.py", line 120, in execute
    cursor.execute(sql, params)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 79, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/backends/utils.py", line 62, in execute
    return self.cursor.execute(sql)
django.db.utils.ProgrammingError: no schema has been selected to create in
LINE 1: CREATE TABLE "django_migrations" ("id" serial NOT NULL PRIMA...
                     ^


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "manage.py", line 29, in <module>
    execute_from_command_line(sys.argv)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/core/management/__init__.py", line 364, in execute_from_command_line
    utility.execute()
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/core/management/__init__.py", line 356, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/core/management/base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/core/management/base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/core/management/commands/migrate.py", line 83, in handle
    executor = MigrationExecutor(connection, self.migration_progress_callback)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/migrations/executor.py", line 20, in __init__
    self.loader = MigrationLoader(self.connection)
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/migrations/loader.py", line 52, in __init__
    self.build_graph()
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/migrations/loader.py", line 209, in build_graph
    self.applied_migrations = recorder.applied_migrations()
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/migrations/recorder.py", line 65, in applied_migrations
    self.ensure_schema()
  File "/Users/kurtpeek/Documents/Dev/lucy2/lucy-web/venv/lib/python3.6/site-packages/django/db/migrations/recorder.py", line 59, in ensure_schema
    raise MigrationSchemaMissing("Unable to create the django_migrations table (%s)" % exc)
django.db.migrations.exceptions.MigrationSchemaMissing: Unable to create the django_migrations table (no schema has been selected to create in
LINE 1: CREATE TABLE "django_migrations" ("id" serial NOT NULL PRIMA...
                     ^
)

根据我对MigrationSchemaMissing(Unable to create the django_migrations table (%s) % exc) 的了解，我需要运行

grant usage on schema public to username;
grant create on schema public to username;

但是，username 应该填写什么？这应该是postgres吗？

以下是有关public 架构和search_path 的更多详细信息：

(venv) Kurts-MacBook-Pro-2:lucy-web kurtpeek$ python manage.py dbshell
psql (10.4)
Type "help" for help.

lucy_prod=> \dn+ public
                        List of schemas
  Name  |  Owner   | Access privileges |      Description       
--------+----------+-------------------+------------------------
 public | postgres |                   | standard public schema
(1 row)

lucy_prod=> SHOW search_path;
   search_path   
-----------------
 "$user", public
(1 row)

更新

通过运行select current_user; 命令，我确定我当前的用户名为lucyapp，但如果我尝试为该用户使用grant usage on schema public，我会收到“权限被拒绝”错误：

lucy_prod=> select current_user;
 current_user 
--------------
 lucyapp
(1 row)

lucy_prod=> grant usage on schema public to lucyapp;
ERROR:  permission denied for schema public
lucy_prod=> grant create on schema public to lucyapp;
ERROR:  permission denied for schema public

Answer 1

这是由于角色对public 架构的访问问题所致。在数据库 shell 中运行此脚本将解决此问题。

GRANT ALL ON SCHEMA public TO your_user;
GRANT ALL ON SCHEMA public TO public;

This is for Postgres DB. A similar script can be found for other SQL DB.

Answer 2

当我简单地使用psql 命令而不是python manage.py dbshell 输入psql 时，我能够GRANT USAGE 和GRANT CREATE。随后我遇到了与数据库中对象的所有者（关系等）相关的错误，而不是DATABASES['USER'] 设置中的对象，即'lucyapp'。

我终于在Postgresql - backup database and restore on different owner? 之后使用pg_restore 和--no-owner 和--role=lucyapp 选项解决了这些问题。