[BangPypers] SQLAlchemy and 'non-trivial' default values for a column

[Dhruv Baldawa]

OK I misread. Let me see if I understood your problem correctly.

   1. All the consultations will be stored in that table.
   2. When you have a Consultation object, you need a `consultation_count`
   property for the number of consultation for that day.

So, this should work now, according to me:

def generate_consultation_id(date):
     return Consultation.query.filter_by(data=data).count() + 1

class Consultation(Base):
    ...
    cid = Column(Integer, default=generate_consultation_id)

This should work, according to me. The function is called while adding the
id to the database.
Reference<http://docs.sqlalchemy.org/en/rel_0_8/core/schema.html#sqlalchemy.schema.Column.__init__>

--
Dhruv Baldawa
(http://www.dhruvb.com)


On Wed, Feb 6, 2013 at 11:47 AM, Sriram Karra <karra.etc at gmail.com> wrote:

> On Wed, Feb 6, 2013 at 11:32 AM, Dhruv Baldawa <dhruvbaldawa at gmail.com
> >wrote:
>
> > I would do a:
> >
> > class Consultation(Base):
> >     __tablename__ = 'consultation'
> >
> >     id         = Column(Integer, primary_key=True)
> >     patient_id = Column(Integer, ForeignKey('patient.id'))
> >     doctor_id  = Column(Integer, ForeignKey('doctor.id'))
> >     date       = Column(Date(),  default=MyT.today())
> >
> >    @property
> >    def consultation_count(self):
> >         ''' returns the consultation count for current date '''
> >         return self.query.filter_by(date=self.date).count() # the syntax
> > might not be correct
> >
> > c = Consultation.query.get(1)
> > print c.consultation_count
> >
> > This way its computed on the fly and you dont need to store it.
> >
>
> If I read your code correctly this would mean:
>
> (a) the consultation_count property for all the consutlations that happened
> on a given day will be the same value
> (b) for a given row this value will keep changing as we insert more records
> into the table.
>
> So this will not work, no?
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