On Oct 30, 2013, at 10:58 AM, jkmacc <jkm...@gmail.com> wrote:
> Hi all,
>
> I've got a module defining a number of abstract declarative classes. They
> represent standard generic classes/tables.
> I'd like to take one of these abstract classes and subclass more than once,
> adding a 'schema' name to '__table_args__' and a '__tablename__'. This to me
> is like making a specific 'realization' of the abstract class structure. I
> want to keep the columns (with info dictionaries) and constraints in the
> abstract class, but make a 'realization' of the abstract class as different
> tables with different names and schema.
>
> When I do this, however, I get warnings and errors I don't understand. Here's
> an example:
>
> % ------------------------ code
> --------------------------------------------------------------------------
> from sqlalchemy import Column, Numeric, String, Date, PrimaryKeyConstraint
> from sqlalchemy.ext.declarative import declarative_base
>
> Base = declarative_base()
>
> class Students(Base):
> __abstract__ = True
> __table_args__ = (PrimaryKeyConstraint(u'stid', u'last_name'),)
>
> stid = Column(Numeric(9, 0, False), nullable=False, info={'format':
> '9.2f'})
> first_name = Column(String(30), info={'format': '30.30s'})
> last_name = Column(String(30), info={'format': '30.30s'})
> description = Column(String(80), info={'format': '80.80s'})
> lddate = Column(Date, info={'format': '%Y-%m-%d %H:%M:%S'})
>
>
> class MyStudents(Students):
> __tablename__ = 'students'
> __table_args__ = Students.__table_args__ + ({'__schema__': 'me'},)
>
> class OldStudents(Students):
> __tablename__ = 'oldstudents'
> __table_args__ = Students.__table_args__ + ({'__schema__': 'me'},)
>
> class OtherStudents(Students):
> __tablename__ = 'students'
> __table_args__ = Students.__table_args__ + ({'__schema__': 'other'},)
> % ------------------------ end code ———————————————————————————————————
well the “schema” argument on Table is called “schema”, not “__schema__”, and
the __table_args__ are not copied to each subclass (e.g. you’re using the same
PrimaryKeyConstraint object on three different Table objects) so you’d want to
use @declared_attr + def __table_args__(cls) for that.
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