ORM 没有挂钩它的生成方式insert()
构造,所以你在这里能做的最好的事情就是拦截insert()
的声明Table
level,这可能已经足够好了,因为您想对这些表进行全面的“忽略”操作,这里有一个使用类装饰器使其通用的方法。我们正在利用执行前 http://docs.sqlalchemy.org/en/rel_0_8/core/events.html#sqlalchemy.events.ConnectionEvents.before_execute这里的事件重写某些insert()
结构体:
from sqlalchemy import event
from sqlalchemy.engine import Engine
from sqlalchemy.sql import Insert
_ignore_tables = set()
@event.listens_for(Engine, "before_execute", retval=True)
def _ignore_insert(conn, element, multiparams, params):
if isinstance(element, Insert) and \
element.table.name in _ignore_tables:
element = element.prefix_with("IGNORE")
return element, multiparams, params
def ignore_inserts(cls):
_ignore_tables.add(cls.__table__.name)
return cls
if __name__ == '__main__':
from sqlalchemy import Column, Integer, create_engine
from sqlalchemy.orm import Session
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class A(Base):
__tablename__ = 'a'
id = Column(Integer, primary_key=True)
@ignore_inserts
class B(Base):
__tablename__ = 'b'
id = Column(Integer, primary_key=True)
@ignore_inserts
class C(Base):
__tablename__ = 'c'
id = Column(Integer, primary_key=True)
e = create_engine("mysql://scott:tiger@localhost/test", echo=True)
Base.metadata.drop_all(e)
Base.metadata.create_all(e)
s = Session(e)
s.add_all([A(), B(), C()])
s.commit()
像这样全面使用它会让我紧张,这里有一个不同的版本,以便您可以使用上下文管理器为具有特定内容的特定表设置规则Session
:
from sqlalchemy import event
from sqlalchemy.engine import Engine
from sqlalchemy.sql import Insert
from contextlib import contextmanager
@event.listens_for(Engine, "before_execute", retval=True)
def _ignore_insert(conn, element, multiparams, params):
if isinstance(element, Insert) and \
'ignore_tables' in conn.info and \
element.table.name in conn.info['ignore_tables']:
element = element.prefix_with("IGNORE")
return element, multiparams, params
@contextmanager
def ignore_inserts(session, names):
conn = session.connection()
info = conn.info # hold onto info so we can still
# get to it when the Connection is closed
previous = info.get('ignore_tables', ())
try:
info['ignore_tables'] = set(names)
yield
finally:
info['ignore_tables'] = previous
if __name__ == '__main__':
from sqlalchemy import Column, Integer, create_engine
from sqlalchemy.orm import Session
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class A(Base):
__tablename__ = 'a'
id = Column(Integer, primary_key=True)
class B(Base):
__tablename__ = 'b'
id = Column(Integer, primary_key=True)
class C(Base):
__tablename__ = 'c'
id = Column(Integer, primary_key=True)
e = create_engine("mysql://scott:tiger@localhost/test", echo=True)
Base.metadata.drop_all(e)
Base.metadata.create_all(e)
s = Session(e)
with ignore_inserts(s, ['b']):
s.add_all([A(), B(), C()])
s.commit()
with ignore_inserts(s, ['a', 'c']):
s.add_all([A(), B(), C()])
s.commit()