我知道关于完全相同的问题还有很多其他问题,但是我已经尝试了他们的答案,到目前为止还没有一个工作。
我试图从与其他表有关系的表中删除记录。这些表中的外键是nullable=false
,因此尝试删除另一个表正在使用的记录应引发异常。
但即使用cat try-except
包围delete语句,错误仍然没有被捕获,所以我怀疑异常可能会在其他地方引发。
我在Pyramid框架中使用SQLite和SQLAlchemy,并且我的会话配置了ZopeTransactionExtension
。
这就是我尝试删除的方式: 在views.py
中from sqlalchemy.exc import IntegrityError
from project.app.models import (
DBSession,
foo)
@view_config(route_name='fooview', renderer='json', permission='view')
def fooview(request):
""" The fooview handles different cases for foo
depending on the http method
"""
if request.method == 'DELETE':
if not request.has_permission('edit'):
return HTTPForbidden()
deleteid = request.matchdict['id']
deletethis = DBSession.query(foo).filter_by(id=deleteid).first()
try:
qry = DBSession.delete(deletethis)
transaction.commit()
if qry == 0:
return HTTPNotFound(text=u'Foo not found')
except IntegrityError:
DBSession.rollback()
return HTTPConflict(text=u'Foo in use')
return HTTPOk()
在models.py中,我设置了DBSession
和我的模型:
from zope.sqlalchemy import ZopeTransactionExtension
from sqlalchemy.orm import (
scoped_session,
sessionmaker,
relationship,
backref,
)
DBSession = scoped_session(sessionmaker(extension=ZopeTransactionExtension('changed')))
Base = declarative_base()
class foo(Base):
""" foo defines a unit used by bar
"""
__tablename__ = 'foo'
id = Column(Integer, primary_key=True)
name = Column(Text(50))
bars = relationship('bar')
class bar(Base):
__tablename__ = 'bar'
id = Column(Integer, primary_key=True)
fooId = Column(Integer, ForeignKey('foo.id'), nullable=False)
foo = relationship('foo')
在__init__.py中我配置了我的会话:
from project.app.models import (
DBSession,
Base,
)
def main(global_config, **settings):
""" This function returns a Pyramid WSGI application.
"""
engine = engine_from_config(settings, 'sqlalchemy.')
# fix for association_table cascade delete issues
engine.dialect.supports_sane_rowcount = engine.dialect.supports_sane_multi_rowcount = False
DBSession.configure(bind=engine)
Base.metadata.bind = engine
使用此设置我
IntegrityError:(IntegrityError)NOT NULL约束失败
追溯here。
如果我将transaction.commit()
替换为DBSession.flush()
,我会
ResourceClosedError:此事务已关闭
如果我删除transaction.commit()
,我仍然会收到相同的错误,但没有明确的起源点。
更新: 我进行了一些鼻子测试,在某些情况下,但不是全部,但是正确处理了异常。
在我的测试中,我导入会话并对其进行配置:
from optimate.app.models import (
DBSession,
Base,
foo)
def _initTestingDB():
""" Build a database with default data
"""
engine = create_engine('sqlite://')
Base.metadata.create_all(engine)
DBSession.configure(bind=engine)
with transaction.manager:
# add test data
class TestFoo(unittest.TestCase):
def setUp(self):
self.config = testing.setUp()
self.session = _initTestingDB()
def tearDown(self):
DBSession.remove()
testing.tearDown()
def _callFUT(self, request):
from project.app.views import fooview
return fooview(request)
def test_delete_foo_keep(self):
request = testing.DummyRequest()
request.method = 'DELETE'
request.matchdict['id'] = 1
response = self._callFUT(request)
# foo is used so it is not deleted
self.assertEqual(response.code, 409)
def test_delete_foo_remove(self):
_registerRoutes(self.config)
request = testing.DummyRequest()
request.method = 'DELETE'
request.matchdict['id'] = 2
response = self._callFUT(request)
# foo is not used so it is deleted
self.assertEqual(response.code, 200)
有谁知道发生了什么?
答案 0 :(得分:2)
你可能只是“做错了”。您的问题涉及两个问题。处理由数据库完整性错误引发的事务级错误,并为应用程序代码/模型/查询建模以实现业务逻辑。我的回答重点是编写符合常见模式的代码,同时使用pyramid_tm
进行事务管理,将sqlalchemy用作ORM。
在金字塔中,如果您已配置会话(脚手架自动为您执行)以使用ZopeTransactionExtension,则在视图执行之后才会刷新/提交会话。 如果您想在视图中自己捕获任何SQL错误,则需要强制刷新以将SQL发送到引擎。 DBSession.flush()应该在delete(...)之后执行。
如果你提出任何4xx / 5xx HTTP返回码,例如金字塔例外HTTPConflict,交易将被中止。
@view_config(route_name='fooview', renderer='json', permission='view')
def fooview(request):
""" The fooview handles different cases for foo
depending on the http method
"""
if request.method == 'DELETE':
if not request.has_permission('edit'):
return HTTPForbidden()
deleteid = request.matchdict['id']
deletethis = DBSession.query(foo).filter_by(id=deleteid).first()
if not deletethis:
raise HTTPNotFound()
try:
DBSession.delete(deletethis)
DBSession.flush()
except IntegrityError as e:
log.debug("delete operation not possible for id {0}".format(deleteid)
raise HTTPConflict(text=u'Foo in use')
return HTTPOk()
此excerpt from todopyramid/models.py突出显示了如何在不使用DBSession
对象的情况下删除集合项。
def delete_todo(self, todo_id):
"""given a todo ID we delete it is contained in user todos
delete from a collection
http://docs.sqlalchemy.org/en/latest/orm/session.html#deleting-from-collections
https://stackoverflow.com/questions/10378468/deleting-an-object-from-collection-in-sqlalchemy"""
todo_item = self.todo_list.filter(
TodoItem.id == todo_id)
todo_item.delete()
这个sample code from pyramid_blogr清楚地显示了删除SQL数据库项目的简单金字塔视图代码的外观。通常您不必与事务进行交互。这是一项功能 - 广告为one the unique feature of pyramid。只需选择任何使用sqlalchemy的金字塔教程,并尽可能地坚持使用模式。如果您在应用程序模型级别解决问题,则事务机制将隐藏在后台,除非您明确需要其服务。
@view_config(route_name='blog_action', match_param="action=delete", permission='delete')
def blog_delete(request):
entry_id = request.params.get('id', -1)
entry = Entry.by_id(entry_id)
if not entry:
return HTTPNotFound()
DBSession.delete(entry)
return HTTPFound(location=request.route_url('home'))
要向应用程序用户提供有意义的错误消息,您可以在数据库模型层或金字塔视图层捕获数据库约束的错误。捕获sqlalchemy异常以提供错误消息可能与此sample code
类似from sqlalchemy.exc import OperationalError as SqlAlchemyOperationalError
@view_config(context=SqlAlchemyOperationalError)
def failed_sqlalchemy(exception, request):
"""catch missing database, logout and redirect to homepage, add flash message with error
implementation inspired by pylons group message
https://groups.google.com/d/msg/pylons-discuss/BUtbPrXizP4/0JhqB2MuoL4J
"""
msg = 'There was an error connecting to database'
request.session.flash(msg, queue='error')
headers = forget(request)
# Send the user back home, everything else is protected
return HTTPFound(request.route_url('home'), headers=headers)
参考
答案 1 :(得分:1)
不确定这是否有帮助 - 我没有从追溯中捕获出错的地方,需要更多时间。但您可以像这样使用事务管理器:
from sqlalchemy.exc import IntegrityError
try:
with transaction.manager:
deletethis = DBSession.query(foo).filter_by(id=deleteid).first()
qry = DBSession.delete(deletethis)
if qry == 0:
return HTTPNotFound()
# transaction.manager commits when with context manager exits here
except IntegrityError:
DBSession.rollback()
return HTTPConflict()
return HTTPOk()