Re: [Sqlalchemy-tickets] [sqlalchemy] #2762: Relationship lazy configuration doesn't work with polymorphism

[sqlalchemy <mi...@zz...>]

#2762: Relationship lazy configuration doesn't work with polymorphism
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      Reporter:  schlamar          |      Owner:  zzzeek
          Type:  defect            |     Status:  closed
      Priority:  medium            |  Milestone:
     Component:  orm               |   Severity:  no triage selected yet
    Resolution:  worksforme        |   Keywords:
Progress State:  completed/closed  |
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Changes (by zzzeek):

 * status:  new => closed
 * resolution:   => worksforme
 * status_field:  awaiting triage => completed/closed


Comment:

 a polymorphic load on joined table inheritance by default only loads from
 the base table, not any of the related tables.  therefore a joined eager
 load from SubModel->related_model is ignored here.

 The solution here is to use `with_polymorphic`, of which there are three
 ways to specify (mapper level, `query.with_polymorphic()`, and the newer
 `with_polymorphic()` standalone function), specifying that loads for
 `Model` should also join out to load submodels of type `SubModel`:

 {{{
 #!python

     session = Session()
     model_with_related = with_polymorphic(Model, SubModel)
     s = session.query(model_with_related).one()
     session.close()
     s.related_model

 # or

     session = Session()
     s = session.query(Model).with_polymorphic(SubModel).one()
     session.close()
     s.related_model

 # or

 Model.__mapper__.with_polymorphic = (SubModel, None)

 }}}

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2762#comment:1>
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