您在上面看到的代码只是一个示例,但它可以重现此错误:
sqlalchemy.exc.IntegrityError: (raised as a result of Query-invoked autoflush;
consider using a session.no_autoflush block if this flush is occurring prematurely)
(sqlite3.IntegrityError) NOT NULL constraint failed: X.nn
[SQL: 'INSERT INTO "X" (nn, val) VALUES (?, ?)'] [parameters: (None, 1)]
映射实例仍添加到会话中.实例想知道(这意味着在数据库上进行查询)是否存在其自身类型具有相同值的其他实例.还有第二个属性/列(_nn
).它被指定为NOT NULL
.但默认情况下是NULL
.
当实例(如示例中)仍然添加到会话中时,调用query.one()
调用自动刷新.此刷新创建一个INSERT
,try 存储实例.这会失败,因为_nn
仍然为空,并且违反了NOT NULL
约束.
这就是我目前的理解.
#!/usr/bin/env python3
import os.path
import os
import sqlalchemy as sa
import sqlalchemy.orm as sao
import sqlalchemy.ext.declarative as sad
from sqlalchemy_utils import create_database
_Base = sad.declarative_base()
session = None
class X(_Base):
__tablename__ = 'X'
_oid = sa.Column('oid', sa.Integer, primary_key=True)
_nn = sa.Column('nn', sa.Integer, nullable=False) # NOT NULL!
_val = sa.Column('val', sa.Integer)
def __init__(self, val):
self._val = val
def test(self, session):
q = session.query(X).filter(X._val == self._val)
x = q.one()
print('x={}'.format(x))
dbfile = 'x.db'
def _create_database():
if os.path.exists(dbfile):
os.remove(dbfile)
engine = sa.create_engine('sqlite:///{}'.format(dbfile), echo=True)
create_database(engine.url)
_Base.metadata.create_all(engine)
return sao.sessionmaker(bind=engine)()
if __name__ == '__main__':
session = _create_database()
for val in range(3):
x = X(val)
x._nn = 0
session.add(x)
session.commit()
x = X(1)
session.add(x)
x.test(session)
当然,解决方案是在调用query.one()
之前将not实例添加到会话中.这项工作.但在我的真实(但对于这个问题来说非常复杂)用例中,这并不是一个好的解决方案.