python - 蒸馏器迁移误差 flask

Question

我正在使用找到的指南制作测试博客 here .它非常全面。但是，我在 alembic 迁移方面遇到了麻烦。我可以删除所有版本，并启动一个包含所有列的新数据库。但是，当我添加一个新列时，我遇到了问题。这是我的 models.py 中的代码:

模型.py

....
class Person(db.Model):
    __tablename__ = 'person'
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(100), unique=True)
    pwdhash = db.Column(db.String(100))
    name = db.Column(db.String(100), unique=True)

    def __init__(self, email, name, password):
        self.email = email
        self.name = name.title()
        self.set_password(password)

    def __repr__(self):
        return '<User %r>' % (self.name)

    def set_password(self, password):
        self.pwdhash = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.pwdhash, password)

    @classmethod
    def all(cls):
        return Person.query.all()

class Category(db.Model):
    __tablename__ = 'category'
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100), unique=True)
    description = db.Column(db.Text)

    def __unicode__(self):
        return self.name

class Article(db.Model):
    __tablename__ = 'articles'
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String(100))
    body = db.Column(db.Text)
    created = db.Column(db.DateTime, default=datetime.datetime.now)
    category_name = db.Column(db.String(10), db.ForeignKey(Category.name))
    category = db.relationship(Category)
    person_name = db.Column(db.String(100), db.ForeignKey(Person.name, onupdate="CASCADE", ondelete="CASCADE"))
    person = db.relationship(Person)

    @property
    def slug(self):
        return urlify(self.title)

    @classmethod
    def all(cls):
        return Article.query.order_by(desc(Article.created)).all()

    @classmethod
    def find_by_category(cls, category):
        return Article.query.filter(Article.category_name == category).all()

这一切都非常标准。但是，如果我要向我的 People 表中添加一个随机列，如下所示:

class Person(db.Model):
    ....
    random_column = db.Column(db.Integer())

然后运行 ​​python manage.py db migrate(工作正常)然后运行 ​​python manage.py db upgrade 然后我收到以下错误:

Traceback (most recent call last):
  File "manage.py", line 7, in <module>
    manager.run()
  File "/Library/Python/2.7/site-packages/flask_script/__init__.py", line 397, in run
    result = self.handle(sys.argv[0], sys.argv[1:])
  File "/Library/Python/2.7/site-packages/flask_script/__init__.py", line 376, in handle
    return handle(app, *positional_args, **kwargs)
  File "/Library/Python/2.7/site-packages/flask_script/commands.py", line 145, in handle
    return self.run(*args, **kwargs)
  File "/Library/Python/2.7/site-packages/flask_migrate/__init__.py", line 82, in upgrade
    command.upgrade(config, revision, sql = sql, tag = tag)
  File "/Library/Python/2.7/site-packages/alembic/command.py", line 124, in upgrade
    script.run_env()
  File "/Library/Python/2.7/site-packages/alembic/script.py", line 199, in run_env
    util.load_python_file(self.dir, 'env.py')
  File "/Library/Python/2.7/site-packages/alembic/util.py", line 198, in load_python_file
    module = load_module(module_id, path)
  File "/Library/Python/2.7/site-packages/alembic/compat.py", line 55, in load_module
    mod = imp.load_source(module_id, path, fp)
  File "migrations/env.py", line 72, in <module>
    run_migrations_online()
  File "migrations/env.py", line 65, in run_migrations_online
    context.run_migrations()
  File "<string>", line 7, in run_migrations
  File "/Library/Python/2.7/site-packages/alembic/environment.py", line 652, in run_migrations
    self.get_context().run_migrations(**kw)
  File "/Library/Python/2.7/site-packages/alembic/migration.py", line 225, in run_migrations
    change(**kw)
  File "migrations/versions/4171a9f6ed2a_.py", line 19, in upgrade
    op.drop_index('category_name_key', 'category')
  File "<string>", line 7, in drop_index
  File "<string>", line 1, in <lambda>
  File "/Library/Python/2.7/site-packages/alembic/util.py", line 293, in go
    return fn(*arg, **kw)
  File "/Library/Python/2.7/site-packages/alembic/operations.py", line 716, in drop_index
    self._index(name, table_name, ['x'], schema=schema)
  File "/Library/Python/2.7/site-packages/alembic/ddl/impl.py", line 164, in drop_index
    self._exec(schema.DropIndex(index))
  File "/Library/Python/2.7/site-packages/alembic/ddl/impl.py", line 76, in _exec
    conn.execute(construct, *multiparams, **params)
  File "/Library/Python/2.7/site-packages/sqlalchemy/engine/base.py", line 662, in execute
    params)
  File "/Library/Python/2.7/site-packages/sqlalchemy/engine/base.py", line 720, in _execute_ddl
    compiled
  File "/Library/Python/2.7/site-packages/sqlalchemy/engine/base.py", line 874, in _execute_context
    context)
  File "/Library/Python/2.7/site-packages/sqlalchemy/engine/base.py", line 1024, in _handle_dbapi_exception
    exc_info
  File "/Library/Python/2.7/site-packages/sqlalchemy/util/compat.py", line 196, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb)
  File "/Library/Python/2.7/site-packages/sqlalchemy/engine/base.py", line 867, in _execute_context
    context)
  File "/Library/Python/2.7/site-packages/sqlalchemy/engine/default.py", line 324, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.InternalError: (InternalError) cannot drop index category_name_key because constraint category_name_key on table category requires it
HINT:  You can drop constraint category_name_key on table category instead.
 '\nDROP INDEX category_name_key' {}

它甚至没有提到我在堆栈跟踪中创建的列的名称，所以这让我相信其他表有问题。它提到删除索引，但我在迁移中没有做任何类似的事情，只是向 People 表添加一列。是我不明白的 alembic 中的东西吗？

就像我说的那样，当我启动一个全新的数据库并加载配置时，它可以完美地找到。只有当我进行更改并尝试迁移时，alembic 才会向我抛出这些错误。有谁知道为什么会这样？

编辑

以防万一人们需要查看我的 config.py 文件:

配置.py

import os
basedir = os.path.abspath(os.path.dirname(__file__))

#-----Config the app
SECRET_KEY = 'my_key'
CSRF_ENABLED = True

#-----Config Database
SQLALCHEMY_DATABASE_URI = 'postgresql://username:changeme@localhost/test'
SQLALCHEMY_COMMIT_ON_TEARDOWN = True
SQLALCHEMY_MIGRATE_REPO = os.path.join(basedir, 'db_repository')

#-----Config Upload folder
UPLOAD_FOLDER = os.path.realpath('./snb/static') + '/uploads'

Answer 1

我关注了the link to the doc在 Flask-Migrate 上查看它是如何使用 alembic 的，它说:

The migrate command adds a new migration script. You should review it and edit it to be accurate, as Alembic cannot detect all changes that you make to your models. In particular it does not detect indexes, so those need to be added manually to the script.

Flask-Migrate 使用称为“自动生成”的 alembic 功能，它会尝试将数据库的状态与模型进行比较并自动创建差异。

我们直接使用 Alembic，我发现自动生成非常方便，但我必须手动编辑很多次，尤其是在处理索引和约束时。

所以我的解决方案是按说明操作并手动编辑迁移文件并删除不需要或虚假的行。