最近在学flask ，我是跟《flask-web开发：基于Python的Web应用开发实战》 这本书一步一步实现的，也就是在github上 flasky 这个项目。中间遇到一两个比较大的问题，记录下来*

flask + heroku +postagres

1. 问题一：

在成功 heroku服务器git后， 初始和更新数据库的时候，如类似以下错误:

heroku run python manager.py deploy # 初始和更新数据库

Running python manager.py deploy on ⬢ flasky-blog-mirui... ⣾ 
Running python manager.py deploy on ⬢ flasky-blog-mirui... ⣷ starting, run.7767 (Free)
Running python manager.py deploy on ⬢ flasky-blog-mirui... up, run.7767 (Free)

INFO  [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO  [alembic.runtime.migration] Will assume transactional DDL.
INFO  [alembic.runtime.migration] Running upgrade  -> 8d6dba4cf1a4, the second migration

psycopg2.errors.UndefinedTable: relation "users" does not exist

sqlalchemy.exc.ProgrammingError: (psycopg2.errors.UndefinedTable) relation "users" does not exist

大致是上面错误，具体看下列错误一**

1. 一开始，看报错提示，以为是自己的 psycopg2出错了（我安装二进制包psycopg2-binary,因为安装不上psycopg2）

2. 以为是数据库 结构有点问题，后面优化数据结构与类型，还是报错。

3. 执行git push heroku master，可以运行，打开APP的链接，只要是动态连接到数据库的页面都会500 Internal Server Error报服务器错。显然是连接数据库出错

4. 执行 heroku logs -t 发现会报类似sqlalchemy.exc.ProgrammingError: (psycopg2.errors.UndefinedTable) relation "posts" does not exist这样的错，与之前一样的错。

5. 本地也使用本地postagres库，一切正常。排除数据库出错，代码问题。

无奈～～，想起之前在 stackoverflow搜索 Internal Server Error+flask+heroku就看到有人说是把migrations版本都删掉,无奈，做个备份，把migrations文件夹删掉，git 和初始化后，居然没有报错，ztyd神奇！

解决方法：

在确定，代码没问题，在本地的虚拟环境正常运行可采取以下操作：

删掉烦人的数据库版本控制migrations文件夹

rm -rf ./migrations
git add .
git commit -am '马上要好了'
git push heroku master
heroku run python manage,py deploy

好了，这就可以打开你的heroku app 了。

欢迎你们来我的 heroku app flasky-blog-mirui ,记得给我留言哦～～～

* 错误一

heroku run python manager.py deploy # 初始和更新数据库
Running python manager.py deploy on ⬢ flasky-blog-mirui... ⣾ 
Running python manager.py deploy on ⬢ flasky-blog-mirui... ⣷ starting, run.7767 (Free)
Running python manager.py deploy on ⬢ flasky-blog-mirui... up, run.7767 (Free)

INFO  [alembic.runtime.migration] Context impl PostgresqlImpl.
INFO  [alembic.runtime.migration] Will assume transactional DDL.
INFO  [alembic.runtime.migration] Running upgrade  -> 8d6dba4cf1a4, the second migration
Traceback (most recent call last):
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1244, in _execute_context
    cursor, statement, parameters, context
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 552, in do_execute
    cursor.execute(statement, parameters)
psycopg2.errors.UndefinedTable: relation "users" does not exist


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

Traceback (most recent call last):
  File "manager.py", line 83, in <module>
    manager.run()
  File "/app/.heroku/python/lib/python3.6/site-packages/flask_script/__init__.py", line 417, in run
    result = self.handle(argv[0], argv[1:])
  File "/app/.heroku/python/lib/python3.6/site-packages/flask_script/__init__.py", line 386, in handle
    res = handle(*args, **config)
  File "/app/.heroku/python/lib/python3.6/site-packages/flask_script/commands.py", line 216, in __call__
    return self.run(*args, **kwargs)
  File "manager.py", line 67, in deploy
    upgrade()
  File "/app/.heroku/python/lib/python3.6/site-packages/flask_migrate/__init__.py", line 95, in wrapped
    f(*args, **kwargs)
  File "/app/.heroku/python/lib/python3.6/site-packages/flask_migrate/__init__.py", line 280, in upgrade
    command.upgrade(config, revision, sql=sql, tag=tag)
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/command.py", line 276, in upgrade
    script.run_env()
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/script/base.py", line 475, 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 90, 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 177, 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 96, in <module>
    run_migrations_online()
  File "migrations/env.py", line 90, in run_migrations_online
    context.run_migrations()
  File "<string>", line 8, in run_migrations
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/runtime/environment.py", line 839, in run_migrations
    self.get_context().run_migrations(**kw)
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/runtime/migration.py", line 362, in run_migrations
    step.migration_fn(**kw)
  File "/app/migrations/versions/8d6dba4cf1a4_the_second_migration.py", line 21, in upgrade
    op.add_column('users', sa.Column('confirmed', sa.Boolean(), nullable=True))
  File "<string>", line 8, in add_column
  File "<string>", line 3, in add_column
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/operations/ops.py", line 1904, in add_column
    return operations.invoke(op)
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/operations/base.py", line 345, in invoke
    return fn(self, operation)
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/operations/toimpl.py", line 131, in add_column
    operations.impl.add_column(table_name, column, schema=schema)
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/ddl/impl.py", line 231, in add_column
    self._exec(base.AddColumn(table_name, column, schema=schema))
  File "/app/.heroku/python/lib/python3.6/site-packages/alembic/ddl/impl.py", line 134, in _exec
    return conn.execute(construct, *multiparams, **params)
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 988, in execute
    return meth(self, multiparams, params)
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/sql/ddl.py", line 72, in _execute_on_connection
    return connection._execute_ddl(self, multiparams, params)
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1050, in _execute_ddl
    compiled,
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1248, in _execute_context
    e, statement, parameters, cursor, context
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1466, in _handle_dbapi_exception
    util.raise_from_cause(sqlalchemy_exception, exc_info)
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 398, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/util/compat.py", line 152, in reraise
    raise value.with_traceback(tb)
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/engine/base.py", line 1244, in _execute_context
    cursor, statement, parameters, context
  File "/app/.heroku/python/lib/python3.6/site-packages/sqlalchemy/engine/default.py", line 552, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.ProgrammingError: (psycopg2.errors.UndefinedTable) relation "users" does not exist