How to log SQL statements and rows returned in sqlalchemy to aid in debugging?

Question

How do I configure sqlalchemy to log the SQL statements that it's making to the database server, and also log the rows returned from those statements? This would be useful for debugging.

Answer 1

Option 1: set the sqlalchemy.engine logger log level to either logging.INFO or logging.DEBUG: e.g.,

>>> 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')

Reference: Configuring Logging

Option 2: use the echo arg when calling sqlalchemy.create_engine():

e.g.,

>>> 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 – if True, the Engine will log all statements as well as a repr() of their parameter lists to the engines logger, which defaults to sys.stdout. The echo attribute of Engine can be modified at any time to turn logging on and off. If set to the string "debug", result rows will be printed to the standard output as well.