尽我所能,我似乎无法正确捕获sqlalchemy IntegrityError:
from sqlalchemy import exc
try:
insert_record()
except exc.IntegrityError, exc:
print exc # this is never called
handle_elegantly() # this is never called
正如人们所期望的那样:
IntegrityError: (IntegrityError) insert or update on table "my_table"
violates foreign key constraint "my_table_some_column_fkey"
我试图明确地说:
from sqlalchemy.exc import IntegrityError
更新:
我找到了一些似乎适合这里发生的事情,在会话被刷新到数据库之后,并且在try
/ except
blocks被执行之后,不会抛出完整性错误:Trying to catch integrity error with SQLAlchemy
然而,在session.flush()
区块中添加try
会产生InvalidRequestError
:
ERROR:root:This Session's transaction has been rolled back due to a previous
exception during flush. To begin a new transaction with this Session,
first issue Session.rollback().
Original exception was: (IntegrityError)
一旦IntegrityError
被提出,无论你是否发现错误,你工作的会话都会失效。由于第二条错误消息指示您,To begin a new transaction with this Session, first issue Session.rollback().
,继续使用会话,您需要发出session.rollback()
我不能肯定地说,但我猜你或你的web框架正在尝试继续使用以某种方式引发IntegrityError的会话。我建议您在捕获异常或session.rollback()
函数后发出handle_elegantly
。
如果你运行下面你会看到我的意思:
from sqlalchemy import types
from sqlalchemy import exc
from sqlalchemy import create_engine
from sqlalchemy.schema import Column
from zope.sqlalchemy import ZopeTransactionExtension
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker, scoped_session
Base = declarative_base()
class User(Base):
__tablename__ = 'user'
name = Column(types.String, primary_key=True)
def handle_elegantly(name):
session = DBSession()
session.add(User(name=name))
session.flush()
print 'Exception elegantly handled!!\n'
def pretend_view(request):
"""Pretend view in a Pyramid application using pyramid_tm"""
session = DBSession()
user = User()
print '\n-------Here we rollback before continuing -------'
try:
session.add(user)
session.flush()
except exc.IntegrityError:
session.rollback()
handle_elegantly('This will run fine')
print '\n------- Here we do not, and this will error -------'
try:
session.add(user)
session.flush()
except exc.IntegrityError:
handle_elegantly('Exception will be raised')
if __name__ == '__main__':
engine = create_engine('sqlite://')
global DBSession
DBSession = scoped_session(
sessionmaker(extension=ZopeTransactionExtension()))
DBSession.configure(bind=engine)
Base.metadata.bind = engine
Base.metadata.create_all()
pretend_view("dummy request")
我在Flask应用程序中有相同的需求,我像下面一样处理它并且它有效:
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy import exc
db = SQLAlchemy(Flask(__name__))
try:
db.session.add(resource)
return db.session.commit()
except exc.IntegrityError as e:
db.session().rollback()
SQLALCHEMY_COMMIT_ON_TEARDOWN = False