如何记录 sqlalchemy 中返回的 SQL 语句和行以帮助调试？

Question

如何配置sqlalchemy 以记录它对数据库服务器所做的SQL 语句，并记录从这些语句返回的行？这对调试很有用。

Answer 1

选项 1：将 sqlalchemy.engine logger 日志级别设置为 logging.INFO 或 logging.DEBUG： 例如，

>>> import logging
>>> logging.basicConfig()
>>> logger = logging.getLogger('sqlalchemy.engine')
>>> logger.setLevel(logging.DEBUG)
>>> session.query(User).all()
2015-01-02 11:54:25,854 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2015-01-02 11:54:25,856 INFO sqlalchemy.engine.base.Engine SELECT users.id AS users_id, users.name AS users_name
FROM users
2015-01-02 11:54:25,857 INFO sqlalchemy.engine.base.Engine {}
2015-01-02 11:54:25,858 DEBUG sqlalchemy.engine.base.Engine Col ('users_id', 'users_name')
2015-01-02 11:54:25,860 DEBUG sqlalchemy.engine.base.Engine Row (1, u'Alice')
2015-01-02 11:54:25,860 DEBUG sqlalchemy.engine.base.Engine Row (2, u'Bob')

参考：Configuring Logging

选项 2：在调用 sqlalchemy.create_engine() 时使用 echo 参数：

例如，

>>> from sqlalchemy import create_engine
>>> from sqlalchemy.orm import sessionmaker
>>> engine = create_engine('postgres://postgres_user:my_password@localhost/my_db',
...                        echo="debug")
>>> Session = sessionmaker(bind=engine)
>>> session = Session()
>>> users = session.query(User).all()
2015-01-02 11:54:25,854 INFO sqlalchemy.engine.base.Engine BEGIN (implicit)
2015-01-02 11:54:25,856 INFO sqlalchemy.engine.base.Engine SELECT users.id AS users_id, users.name AS users_name
FROM users
2015-01-02 11:54:25,857 INFO sqlalchemy.engine.base.Engine {}
2015-01-02 11:54:25,858 DEBUG sqlalchemy.engine.base.Engine Col ('users_id', 'users_name')
2015-01-02 11:54:25,860 DEBUG sqlalchemy.engine.base.Engine Row (1, u'Alice')
2015-01-02 11:54:25,860 DEBUG sqlalchemy.engine.base.Engine Row (2, u'Bob')

Per the sqlalchemy documentation:

*sqlalchemy.create_engine (*args, **kwargs)
...
echo=False – 如果为 True，引擎会将所有语句及其参数列表的 repr() 记录到引擎记录器，默认为 sys.stdout。 Engine的echo属性可以随时修改开启和关闭登录。如果设置为字符串“debug”，结果行也将打印到标准输出。