python - SQLAlchemy session 错误 : InvalidRequestError

Question

我试图同时从数据库提交和查询结果，但我遇到了这个错误。

sqlalchemy.exc.InvalidRequestError: This session is in 'committed' state; no further SQL can be emitted within this transaction.

完整回溯:

Traceback (most recent call last):
  File "C:\Python34\lib\site-packages\flask\app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
  File "C:\Python34\lib\site-packages\flask\app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "C:\Python34\lib\site-packages\flask\app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "C:\Python34\lib\site-packages\flask\_compat.py", line 33, in reraise
    raise value
  File "C:\Python34\lib\site-packages\flask\app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "C:\Python34\lib\site-packages\flask\app.py", line 1477, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "C:\Python34\lib\site-packages\flask\app.py", line 1381, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "C:\Python34\lib\site-packages\flask\_compat.py", line 33, in reraise
    raise value
  File "C:\Python34\lib\site-packages\flask\app.py", line 1473, in full_dispatch_request
    rv = self.preprocess_request()
  File "C:\Python34\lib\site-packages\flask\app.py", line 1666, in preprocess_request
    rv = func()
  File "C:\Users\Ajay\PycharmProjects\Pypix-Flask\codehackr\auth\views.py", line 14, in before_request
    if current_user.is_authenticated():
  File "C:\Python34\lib\site-packages\werkzeug\local.py", line 338, in __getattr__
    return getattr(self._get_current_object(), name)
  File "C:\Python34\lib\site-packages\werkzeug\local.py", line 297, in _get_current_object
    return self.__local()
  File "C:\Python34\lib\site-packages\flask_login.py", line 46, in <lambda>
    current_user = LocalProxy(lambda: _get_user())
  File "C:\Python34\lib\site-packages\flask_login.py", line 794, in _get_user
    current_app.login_manager._load_user()
  File "C:\Python34\lib\site-packages\flask_login.py", line 363, in _load_user
    return self.reload_user()
  File "C:\Python34\lib\site-packages\flask_login.py", line 325, in reload_user
    user = self.user_callback(user_id)
  File "C:\Users\Ajay\PycharmProjects\Pypix-Flask\codehackr\models.py", line 296, in load_user
    u = db.session.query(User, unread_count).filter(User.id == user_id).first()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\query.py", line 2333, in first
    ret = list(self[0:1])
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\query.py", line 2200, in __getitem__
    return list(res)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\query.py", line 2404, in __iter__
    return self._execute_and_instances(context)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\query.py", line 2417, in _execute_and_instances
    close_with_result=True)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\query.py", line 2408, in _connection_from_session
    **kw)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 843, in connection
    close_with_result=close_with_result)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 847, in _connection_for_bind
    return self.transaction._connection_for_bind(engine)
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 298, in _connection_for_bind
    self._assert_active()
  File "C:\Python34\lib\site-packages\sqlalchemy\orm\session.py", line 192, in _assert_active
    "This session is in 'committed' state; no further "
sqlalchemy.exc.InvalidRequestError: This session is in 'committed' state; no further SQL can be emitted within this transaction.

View .py

@main.route('/user/<username>', methods=['GET','POST'])
def user(username):
    form = SkillForm()
    if form.validate_on_submit():
        skill_add = Skill(skill=form.skill.data, author=current_user._get_current_object())
        db.session.add(skill_add)
        return redirect(url_for('main.index'))
    user = User.query.filter_by(username=username).first_or_404()
    page = request.args.get('page', 1, type=int)
    pagination = user.posts.order_by(Post.timestamp.desc()).paginate(
        page, per_page=current_app.config['POSTS_PER_PAGE'],
        error_out=False)
    posts = pagination.items
    skills = user.skills.all()
    return render_template('user/user.html', user=user, posts=posts,
                           pagination=pagination, form=form, skills=skills)

如何解决这个错误。谢谢

Answer 1

由于您已通过 db.session.add() 将一些对象添加到 session 中，因此您必须首先提交这些更改或回滚它们，以便能够使用此进行查询同一 session 。

db.session.add(skill_add)
db.session.commit() # add this line
return redirect(url_for('main.index'))

添加指定的行可能会导致您的代码按预期工作。

此外，虽然您正在添加技能，查询用户，但会引发此错误，因为这两者受关系约束，因此当您查询用户时，您也会查询该用户拥有的技能。