On Sep 15, 11:03 pm, Jarrod Chesney <jarrod.ches...@gmail.com> wrote:
> Hi All
> I've been reading the documentation for ages and i can't figure out
> why when i print the results a query from my inherited table, It just
> prints them as the base type.
>
> I was hoping someone here would be nice enough to help me solve this
> problem.
>
> I thought the last print statement would print an instance of the
> _UtConfReconcilerActionSnapshot class but it doesn't
>
> I've got one record in both tables and 'id' = 1 in each table.
> What am i doing wrong?
You are missing "polymorphic_on" in
_UtConfReconcilerActions.__mapper_args__. Without this, SQLAlchemy
cannot do polymorphic loads. Try this as your __mapper_args__:
{'polymorphic_on': 'object_type', 'with_polymorphic': '*'}
Hope it helps,
-Conor
> <<<<<<<<<<< Begin code >>>>>>>>>>>>>
>
> from sqlalchemy import Table, Column, Integer, String, MetaData,
> ForeignKey, CheckConstraint
> from sqlalchemy.orm import relation
> from sqlalchemy.ext.declarative import declarative_base
> from sqlalchemy import create_engine
> from sqlalchemy.orm import sessionmaker
>
> __DATABASE_NAME__='UtConfSom.sqlite'
>
> Base = declarative_base()
>
> # ============================== Reconciler Actions
> ===========================
>
> class _UtConfReconcilerActions(Base):
>
> __tablename__ = 'tblReconcilerActions'
> __mapper_args__ = {'with_polymorphic': '*'}
>
> # 1 to Many relationship to the managed
> id = Column(Integer, primary_key=True)
> action = Column(String, CheckConstraint("action in ('SNAPSHOT',
> 'COMPARE', 'UPGRADE')"))
> object_type = Column(String, CheckConstraint("object_type in ('ALL',
> 'SCHEMA', 'TABLE', 'COLUMN', 'INDEX')"))
>
> def __repr__(self):
> return ("'%s'" % _UtConfReconcilerActions.__name__
> + "\n id='%i'" % self.id
> + "\n managed_id='%i'" % self.managed_id
> + "\n action='%s'" % self.action
> + "\n object_type='%s'" % self.object_type
> )
>
> class _UtConfReconcilerActionSnapshot(_UtConfReconcilerActions):
>
> __tablename__ = 'tblReconcilerActionSnapshot'
> # __mapper_args__ = {'with_polymorphic': '*'}
> __mapper_args__ = {'polymorphic_identity': 'snapshot',
> 'with_polymorphic': '*'}
>
> # Joined table inheritence
> id = Column(Integer, ForeignKey('tblReconcilerActions.id'),
> primary_key=True)
>
> revision = Column(String)
> comment = Column(String)
>
> def __repr__(self):
> return (_UtConfReconcilerActions.__repr__(self)
> + "\n '%s'" %
> _UtConfReconcilerActionSnapshot.__name__
> + "\n id='%s'" % self.revision
> + "\n revision='%s'" % self.revision
> )
>
> __db_exists = os.path.exists(__DATABASE_NAME__)
>
> engine = create_engine('sqlite:///' + __DATABASE_NAME__)
>
> # New database, create the tables
> if not __db_exists:
> Base.metadata.create_all(engine)
> print >> sys.stderr, ("WARINING - Creating empty '%s' database" %
> __DATABASE_NAME__ )
>
> Session = sessionmaker(bind=engine)
> session = Session()
>
> print session.query(_UtConfReconcilerActions).with_polymorphic
> ('*').first()
>
> <<<<<<<<<<<<<< end code >>>>>>>>>>>>>>>>>>
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