sqlite - Flask-SQLAlchemy:如何更改表结构？

Question

我在 flask 应用程序中有一个表格模型:

class Article(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    title = db.Column(db.String(80), nullable=False)
    body = db.Column(db.Text, nullable=False)
    pubDate = db.Column(db.DateTime, nullable=False, default=datetime.datetime.now())

然后我使用 db.crate_all() 和 db.add()/db.session 向上表添加一些数据，工作顺利!

然后我想更新和添加类文章的一些属性:

class Article(db.Model):
    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    title = db.Column(db.String(80), nullable=False)
    body = db.Column(db.Text, nullable=False)
    createDate = db.Column(db.DateTime, nullable=False, default=datetime.datetime.now())
    touchDate = db.Column(db.DateTime, nullable=False, default=datetime.datetime.now())
    publishDate = db.Column(db.DateTime, nullable=False, default=datetime.datetime.now())
    isVisible = db.Column(db.Boolean, nullable=False, default=True)
    isDraft = db.Column(db.Boolean, nullable=False, default=True)

更新类文章后，我再次使用 db.create_all()。当我运行我的 flask 应用程序时，我收到以下错误消息:

cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (sqlite3.OperationalError) no such column: article.createDate
[SQL: SELECT article.id AS article_id, article.title AS article_title, article.body AS article_body, article."createDate" AS "article_createDate", article."touchDate" AS "article_touchDate", article."publishDate" AS "article_publishDate", article."isVisible" AS "article_isVisible", article."isDraft" AS "article_isDraft" 
FROM article 
WHERE article."isVisible" = 1]

每当我更改 db.Model 子类时，数据库中的表会自动同步吗？ db.Model子类的属性改变后需要做什么操作？

Answer 1

对于工业级解决方案，Flask-Migrate是一个扩展，使用 Alembic 处理 Flask 应用程序的 SQLAlchemy 数据库迁移.

Alembic is a database migration tool written by the author of SQLAlchemy. A migrations tool offers the following functionality:

• Can emit ALTER statements to a database in order to change the structure of tables and other constructs
• Provides a system whereby “migration scripts” may be constructed; each script indicates a particular series of steps that can “upgrade” a target database to a new version, and optionally a series of steps that can “downgrade” similarly, doing the same steps in reverse.
• Allows the scripts to execute in some sequential manner.

也可以执行原始 SQL ALTER TABLE 语句。

参见 How to execute raw SQL in Flask-SQLAlchemy app