On Jan 3, 2012, at 4:14 PM, sector119 wrote:
> Now I get
>
> File "/home/eps/devel/tourclub/sqlalchemy/lib/sqlalchemy/sql/visitors.py",
> line 59, in _compiler_dispatch
> return getter(visitor)(self, **kw)
> File "/home/eps/devel/tourclub/sqlalchemy/lib/sqlalchemy/sql/compiler.py",
> line 370, in visit_column
> raise exc.CompileError("Cannot compile Column object until "
> CompileError: Cannot compile Column object until it's 'name' is assigned.
>
> With
>
> case([(cls.last_read != None, cls.last_read <= func.now() -
> datetime.timedelta(minutes=30))], else_=literal(False))
> case([(cls.last_read != None, literal(cls.last_read <= func.now() -
> datetime.timedelta(minutes=30)))], else_=literal(False))
> case([(cls.last_read != None, literal(cls.last_read <= func.now() -
> datetime.timedelta(minutes=30)).label('foo'))], else_=literal(False))
please forego the usage of column_property() here in favor of a hybrid. An
example is attached, and the SQLAlchemy documentation is being updated right
now to stress that hybrids should be used unless there's a specific performance
advantage to column_property().
>
>
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from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.hybrid import hybrid_property
import datetime
Base= declarative_base()
class UserMixin(object):
id = Column(Integer, primary_key=True)
username = Column(String(255), unique=True, nullable=False)
last_read = Column("last_read", DateTime)
@hybrid_property
def is_online(self):
if self.last_read is not None:
return self.last_read <= \
datetime.datetime.now() - \
datetime.timedelta(minutes=30)
else:
return False
@is_online.expression
def is_online(cls):
return case([(cls.last_read != None,
cls.last_read <= func.now() -
datetime.timedelta(minutes=30))], else_=literal(False))
class User(UserMixin, Base):
__tablename__ = 'user'
s = Session()
print s.query(User.is_online)
