Hi,
I get away with stuffing datetime.datetime.now() into a DateTime
(timezone=True) column, despite the former being timezone-naive
(.utcoffset() is None, .tzinfo is None, etc.).
It is stored in the table with UTC offset +00, which is arguably
incorrect (states information that was not present in the input).
But even if you call it correct, you get in trouble when you read the
value back as an attribute of a mapped class in a session, set the
attribute again to datetime.datetime.now() (again timezone-naive), and
then try to query the session for the same object again. This retches
up a TypeError: “can't compare offset-naive and offset-aware
datetimes”.
Code to reproduce:
from sqlalchemy import Table, MetaData, Column, Integer, DateTime,
create_engine
from sqlalchemy.orm import sessionmaker, mapper
from datetime import datetime, timedelta
from pytz import utc
t = Table('foo', MetaData(), Column('id', Integer, primary_key=True,),
Column('dt', DateTime(timezone=True)))
class T(object):
pass
mapper(T, t)
e = create_engine('postgres://localhost/satest')
t.create(bind=e, checkfirst=True)
e.execute(t.delete()) # in case we are re-running this test
Session = sessionmaker(bind=e)
inst = T()
inst.dt = datetime.now()
assert inst.dt.utcoffset() is None
session = Session()
session.add(inst)
session.commit()
session.close()
session = Session()
inst = session.query(T).first()
assert inst.dt.utcoffset() == timedelta(0)
inst.dt = datetime.now()
assert inst.dt.utcoffset() is None
# next line raises TypeError: can't compare offset-naive and offset-
aware datetimes
inst = session.query(T).first()
SQLAlchemy should either reject the timezone-naive datetime value
right away when it is bound to a timezone-savvy DateTime column, or
tolerate me setting a timezone-naive datetime value again. I root for
the former.
Regards,
- Gulli
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