Hello.
> It seems like I have to choose, D can either be a polymorphic child or it can
> be
> a parent - it can't be both.
>
> Do I have any options here?
I am almost sure you are correct. This is not possible in SA so you have to
flatten your hierarchy.
I don't know about experiences with inheritance of others on this list, but mine
in SA0.7.9 is not that good. I encountered various limitations along the way. I
guess it dependes on the complexity of the queries. We plan to get rid of it
eventually in our app. However, if I am not mistaken, SA0.8 addresses all the
quirks.
Ladislav Lenart
On 4.6.2013 07:55, Amir Elaguizy wrote:
> Hi there,
>
> I have a tree that looks like this, reflected via polymorphic inheritance:
>
>
> A
> / | \
> B C D
>
> That works great, like:
>
>
> class BaseModel(db.Model): # Table A in diagram
> __tablename__ = "entities"
>
> id = db.Column(db.BigInteger, primary_key=True, nullable=False,
> server_default=func.nextval('guid_seq'))
> type_id = db.Column(db.SmallInteger, db.ForeignKey(EntityTypesModel.id))
>
> __mapper_args__ = {
> 'polymorphic_identity':'entity',
> 'polymorphic_on':type_id,
> 'with_polymorphic':'*'
> }
>
> class BrandModel(BaseModel): # Table B, C, D in diagram
> __tablename__ = 'brands'
>
> id = db.Column(db.BigInteger, db.ForeignKey(StufffModel.id),
> primary_key=True, nullable=False)
> name = db.Column(db.String, nullable=False)
>
> __mapper_args__ = {
> 'polymorphic_identity':ET_BRAND,
> }
>
>
> The problem is I need to reflect something more like this:
>
> A
> / | \
> B C D
> / \
> E F
>
> Where D is not only a polymorphic child of A but also the polymorphic parents
> of
> E & F.
>
> It seems like I have to choose, D can either be a polymorphic child or it can
> be
> a parent - it can't be both.
>
> Do I have any options here?
>
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