我已经成功地在Heroku中部署了一个应用程序，我使用Python和Flask构建。在本地，用户注册和身份验证按预期工作。但是，当我尝试注册或甚至登录到部署的应用程序时，heroku logs--ail显示此错误：

sqlalchemy.exc.ProgrammingError: (psycopg2.errors.UndefinedTable) relation "user" does not exist
2020-10-04T05:30:18.432952+00:00 app[web.1]: LINE 2: FROM "user"
2020-10-04T05:30:18.432952+00:00 app[web.1]: ^
2020-10-04T05:30:18.432953+00:00 app[web.1]: 
2020-10-04T05:30:18.432953+00:00 app[web.1]: [SQL: SELECT "user".id AS user_id, "user".username AS user_username, "user".email AS user_email, "user".password_hash AS user_password_hash, "user".about_me AS user_about_me, "user".last_seen AS user_last_seen
2020-10-04T05:30:18.432954+00:00 app[web.1]: FROM "user"
2020-10-04T05:30:18.432954+00:00 app[web.1]: WHERE "user".username = %(username_1)s
2020-10-04T05:30:18.432954+00:00 app[web.1]: LIMIT %(param_1)s]
2020-10-04T05:30:18.432955+00:00 app[web.1]: [parameters: {'username_1': 'harry', 'param_1': 1}]
2020-10-04T05:30:18.432960+00:00 app[web.1]: (Background on this error at: http://sqlalche.me/e/f405)

因此，我查看了数据库的状态，并注意到数据库中的表（我有用户和帖子）没有更新。我跑了：

$ heroku pg:info DATABASE

=== DATABASE_URL
Plan:                  Hobby-dev
Status:                Available
Connections:           1/20
PG Version:            12.4
Created:               2020-10-05 01:07 UTC
Data Size:             7.9 MB
Tables:                0
Rows:                  0/10000 (In compliance)
Fork/Follow:           Unsupported
Rollback:              Unsupported
Continuous Protection: Off
Add-on:                postgresql-solid-77130

我的本地数据库是SQLite，它将数据保存在本地磁盘上。我切换到PostgreSQL作为推荐我的Heroku得到一个插件，并成功地创建了一个DATABASE_URL。当我比较我的终端结果时，我可以确认数据库URL：

$ heroku config:get DATABASE_URL

在Heroku仪表板上的插件概述中显示。此时，我有了数据库的URL。要更新我的数据库，我运行：

$ heroku run flask db upgrade

这应该会更新我的表，但不会。相反，我得到了一个错误：

Traceback (most recent call last):
  File "/app/.heroku/python/bin/flask", line 8, in <module>
    sys.exit(main())
  File "/app/.heroku/python/lib/python3.6/site-packages/flask/cli.py", line 967, in main
    cli.main(args=sys.argv[1:], prog_name="python -m flask" if as_module else None)
  File "/app/.heroku/python/lib/python3.6/site-packages/flask/cli.py", line 586, in main
    return super(FlaskGroup, self).main(*args, **kwargs)
  File "/app/.heroku/python/lib/python3.6/site-packages/click/core.py", line 782, in main
    rv = self.invoke(ctx)
  File "/app/.heroku/python/lib/python3.6/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/app/.heroku/python/lib/python3.6/site-packages/click/core.py", line 1259, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/app/.heroku/python/lib/python3.6/site-packages/click/core.py", line 1066, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/app/.heroku/python/lib/python3.6/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/app/.heroku/python/lib/python3.6/site-packages/click/decorators.py", line 21, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/app/.heroku/python/lib/python3.6/site-packages/flask/cli.py", line 426, in decorator
    return __ctx.invoke(f, *args, **kwargs)
  File "/app/.heroku/python/lib/python3.6/site-packages/click/core.py", line 610, in invoke
    return callback(*args, **kwargs)
  File "/app/.heroku/python/lib/python3.6/site-packages/flask_migrate/cli.py", line 134, in upgrade
    _upgrade(directory, revision, sql, tag, x_arg)
  File "/app/.heroku/python/lib/python3.6/site-packages/flask_migrate/__init__.py", line 96, in wrapped
    f(*args, **kwargs)
  File "/app/.heroku/python/lib/python3.6/site-packages/flask_migrate/__init__.py", line 271, in upgrade
    command.upgrade(config, revision, sql=sql, tag=tag)
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/command.py", line 298, in upgrade
    script.run_env()
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/script/base.py", line 489, in run_env
    util.load_python_file(self.dir, "env.py")
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/util/pyfiles.py", line 98, in load_python_file
    module = load_module_py(module_id, path)
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/util/compat.py", line 184, in load_module_py
    spec.loader.exec_module(module)
  File "<frozen importlib._bootstrap_external>", line 678, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "migrations/env.py", line 27, in <module>
    str(current_app.extensions['migrate'].db.engine.url).replace('%', '%%'))
AttributeError: 'NoneType' object has no attribute 'engine'

我认为升级就是问题所在，因此出现错误AttributeError:'NoneType'对象没有属性'engine'

我怎样才能解决这个问题？

我试过：

$ heroku pg:push mylocaldb HEROKU_POSTGRESQL_MAGENTA --app sushi

...用我自己的价值观替换占位符，但它仍然不起作用。SO还有其他类似的数据库相关问题，比如这个和这个，但是没有一个真正回答我的问题。