如何在Django中访问远程PostgreSQL数据库服务器（只读事务）？

Question

I have a PostgreSQL database server which is read only transaction. I need to extract some from this database in Django. My setting.py file is given below:

{
  {
    DATABASES = {
      'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'supercaller',
        'USER' : 'chandra_m',
        'PASSWORD' : 'XXXXX',
        'HOST': 'xx.xxx.xxx.xxx',
        'PORT': '5432',
      }
    }
  }
}

I am running the server with python manage.py runserver . I am getting following error

  System check identified no issues (0 silenced).
  Unhandled exception in thread started by <function wrapper at 0x1aa9230>
  Traceback (most recent call last):
   File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-   
   packages/django/utils/autoreload.py", line 222, in wrapper
   fn(*args, **kwargs)
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site - 
  packages/django/core/management/commands/runserver.py", line 107, in inner_run
    self.check_migrations()
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/core/management/commands/runserver.py", line 159, in check_migrations
    executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/migrations/executor.py", line 17, in __init__
    self.loader = MigrationLoader(self.connection)
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/migrations/loader.py", line 48, in __init__
    self.build_graph()
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/migrations/loader.py", line 179, in build_graph
    self.applied_migrations = recorder.applied_migrations()
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/migrations/recorder.py", line 59, in applied_migrations
    self.ensure_schema()
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/migrations/recorder.py", line 53, in ensure_schema
    editor.create_model(self.Migration)
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/backends/schema.py", line 270, in create_model
    self.execute(sql, params)
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/backends/schema.py", line 98, in execute
    cursor.execute(sql, params)
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site- 
  packages/django/db/backends/utils.py", line 81, in execute
    return super(CursorDebugWrapper, self).execute(sql, params)
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site- 
  packages/django/db/utils.py", line 94, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "/home/birendra/knowlarity/chandra/NodetoDjango/venv/local/lib/python2.7/site-
  packages/django/db/backends/utils.py", line 65, in execute
    return self.cursor.execute(sql, params)
  django.db.utils.InternalError: cannot execute CREATE TABLE in a read-only transaction

However, I am able to access this database server through a shell prompt with

psql -h 46.xxx.xxx.52 supercaller chandra_m

How to fix the errors?

Answer 1

you need to make sure your sessions are not using databases (default). I would consider leaving the 'default' to a writeable databaes, then add a 'readonly' database connection as an alternative connection for the objects that you are accessing in it.

Answer 2

First your log says, you have migrations that's not applied to the db you are connecting to, so fix it first.

Then I had success with the following in settings.py SESSION_ENGINE="django.contrib.sessions.backends.cache"