The @expression as column thing is a bit confusing since in the correlated
subquery example in the hybrid attribute section, it looks like you are
returning a select? Does the .label() effectively turn it into a column?
class User(Base):
__tablename__ = 'user'
id = Column(Integer, primary_key=True)
name = Column(String(100), nullable=False)
accounts = relationship("SavingsAccount", backref="owner")
@hybrid_property
def balance(self):
return sum(acc.balance for acc in self.accounts)
@balance.expression
def balance(cls):
return select([func.sum(SavingsAccount.balance)]).\
where(SavingsAccount.user_id==cls.id).\
label('total_balance')
On Friday, July 29, 2016 at 5:29:45 PM UTC-4, Brian Cherinka wrote:
>
>
> Oh interesting. I didn't know that about the @expression. I'll play
> around with the as_scalar() as well, and see if I can get something to
> work.
>
> class Wavelength(Base):
> __tablename__ = 'wavelength'
> __table_args__ = {'autoload': True, 'schema': 'mangadatadb',
> 'extend_existing': True}
>
>
> wavelength = deferred(Column(ARRAY_D(Float, zero_indexes=True)))
>
>
> The wavelength table has a single row and single column, which is an
> array.
>
> The other table of interest would look something like
>
> class NSA(Base):
> __tablename__ = 'nsa'
> __table_args__ = ({'autoload': True, 'schema': 'mangasampledb'})
>
>
> z = Column(Float)
>
>
> This table basically has a float column that corresponds to objects in the
> main cube (object) table. Each float value is used to modify the array in
> wavelength to a unique array for that object.
>
> The Cube class joins to NSA via two tables that are just intermediate
> linking tables for this purpose Cube -> Table A -> Table AToB - > Table B
> (NSA)
>
> class MangaTarget(Base):
> __tablename__ = 'manga_target'
> __table_args__ = {'autoload': True, 'schema': 'mangasampledb'}
>
>
> class MangaTargetToNSA(Base):
> __tablename__ = 'manga_target_to_nsa'
> __table_args__ = (
> ForeignKeyConstraint(['manga_target_pk'],
> ['mangasampledb.manga_target.pk']),
> ForeignKeyConstraint(['nsa_pk'], ['mangasampledb.nsa.pk']),
> {'autoload': True, 'schema': 'mangasampledb'})
>
>
> The rest can probably be hacked together. Let me know if you need
> anything else.
>
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