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POsqlalchemy nested inheritance / polymorphic relationships
 

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    <p>I have a tree that looks like this, reflected via polymorphic inheritance:</p> <pre><code> A / | \ B C D </code></pre> <p>That works great, like:</p> <pre><code>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, } </code></pre> <p>The problem is I need to reflect something more like this:</p> <pre><code> A / | \ B C D / \ E F </code></pre> <p>Where D is not only a polymorphic child of A but also the polymorphic parents of E &amp; F.</p> <p>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.</p> <p>Do I have any options here?</p> <p>EDIT:</p> <p>Just to tie this off, I ended up flattening the tree so it looks like:</p> <pre><code> A / | \ \ B C E F </code></pre> <p>D is now gone and the functionality it provided is in the children (E &amp; F). I'll probably make the common parts a mixin or something.</p> <p>Unfortunate but I couldn't spend more time on this particular issue.</p>
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