Question

当我将测试用户添加到User表时，它会添加正常，即使我执行db.session.add(u)也没问题，但是当我执行db.session.commit()时它会抛出错误。

from app import db

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.Integer(120), unique=True)
    email = db.Column(db.Integer(120), unique=True)
    configkey = db.Column(db.Integer(200), unique=True)
    dob = db.Column(db.DateTime)
    country = db.Column(db.Integer(120))
    friends = db.relationship('Friend', backref = 'friendof', lazy = 'dynamic')


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

class Friend(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.Integer(120), unique=True)
    email = db.Column(db.Integer(120), unique=True)
    dob = db.Column(db.DateTime)
    country = db.Column(db.Integer(120))
    lastmessage = db.Column(db.Integer(1500))
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))


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

- 编辑，包括Python控制台中的错误消息：

>>> u = models.User(name="sd", email="e")                                                                                                                      
>>> db.session.add(u)
>>> db.session.commit()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/scoping.py", line 149, in do
    return getattr(self.registry(), name)(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 721, in commit
    self.transaction.commit()
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 354, in commit
    self._prepare_impl()
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 334, in _prepare_impl
    self.session.flush()
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 1818, in flush
    self._flush(objects)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 1936, in _flush
    transaction.rollback(_capture_exception=True)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/util/langhelpers.py", line 58, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/session.py", line 1900, in _flush
    flush_context.execute()
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/unitofwork.py", line 372, in execute
    rec.execute(self)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/unitofwork.py", line 525, in execute
    uow
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/persistence.py", line 64, in save_obj
    table, insert)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/orm/persistence.py", line 569, in _emit_insert_statements
    execute(statement, params)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 662, in execute
    params)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 761, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 874, in _execute_context
    context)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1024, in _handle_dbapi_exception
    exc_info
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/util/compat.py", line 196, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 867, in _execute_context
    context)
  File "/usr/local/lib/python2.7/dist-packages/sqlalchemy/engine/default.py", line 324, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.OperationalError: (OperationalError) no such table: user u'INSERT INTO user (name, email, configkey, dob, country) VALUES (?, ?, ?, ?, ?)' ('sd'
, 'e', None, None, None)

Answer 1

我正在查看你的堆栈跟踪（特别是最后一行），看起来好像你的表还没有存在。

在将新模型与数据库一起使用之前，必须存在表和列。好消息是SQLAlchemy可以为您做到这一点。

尝试从程序中的任何位置调用以下内容：

# Creates the schema on the database
db.create_all()

请务必在完成后将其删除！

理想情况下，您可以从命令行调用另一个文件来导入您的烧瓶应用程序，然后运行此命令。例如......

# Replace these with your main file and the name of your flask object
from myapp import app 
# And this one with the name of your database file and object
from database import db 

db.create_all()

print "Database ready!"

修改
db.create_all()命令无法修改现有表格，类似的表格在您运行db.create_all()后无法自动更改自己。但是，您可以创建一个新表，然后重新运行该函数并使其显示。

为了正确处理数据库的升级，我建议您查看Flask-Migrate，特别是如果您的应用最终将在生产环境中使用。

我在初始开发过程中使用的快速而脏的方法是删除数据库并在更改过大时再次创建它。

Flask和SQLAlchemy db.session.com不能正常工作

1 个答案: