There's no point in really having the visible_id on the A table, other than
for inheritance.
The point of it being on B (and C, D, E, F, etc.) is that they have unique
sequences populating those "Visible IDs", so I have can have a B-1 and a
C-1 and a D-1.
In other words I have my parent table A with
id, visible_id, type
1, 1, "B"
2, 2, "C"
3, 3, "D"
4, 4, "E"
B
id, visible_id
-----------
1, 1
C
id, visible_id
------------
2, 1
etc.
The alternative (I suppose) would be somehow configuring A.visible_id to
use a different sequence for every child class table, although a.) i dont
know if you can do that and b.) it's less desirable to have duplicate
values in that column.
On Friday, February 14, 2020 at 12:55:47 PM UTC-5, Simon King wrote:
>
> On Fri, Feb 14, 2020 at 5:35 PM Mark Aquino <maqui...@gmail.com
> <javascript:>> wrote:
> >
> > I have a polymorphic class structure like this, with a lot of classes
> extending the parent class.
> > In reality I'm using a Mixin that declares the visible_id column and
> it's defined with @declared_attr.cascading, but for simplicity:
> >
> >
> >
> > class A(Base):
> > __tablename__ = 'a'
> > id = Column(Integer, primary_key=True)
> > visible_id = Column(Integer)
> >
> > class B(A):
> > __tablename__ = 'b'
> > id = Column(Integer, ForeignKey("A.id"), primary_key=True)
> > visible_id = Column(Integer)
> >
> >
> > What I need for my application is to query A.visible_id and return the
> CHILD values for B.visible_id (and all the others).
> >
> > The inheritance works fine, i.e. if i query all As in the database, my
> response is a list of [B] objects, but unless I directly query B the
> visible_id from A takes precedence and I cannot query A.visible_id if I
> remove it from A.
> >
> > Can anyone tell me how to configure this?
> >
>
> Out of interest, what is the point of having a visible_id column in
> the B table? I'm having difficulty imagining what it would mean to
> have an instance of B (which due to inheritance is also an instance of
> A) which has different values in A.visible_id and B.visible_id.
>
> Simon
>
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