Re: [Sqlalchemy-tickets] [sqlalchemy] #2908: Regression in 0.9.x for polymorphic query

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

#2908: Regression in 0.9.x for polymorphic query
---------------------------------+-------------------------------
      Reporter:  jeremy.skippen  |      Owner:  zzzeek
          Type:  defect          |     Status:  new
      Priority:  highest         |  Milestone:  0.9.xx
     Component:  orm             |   Severity:  major - 1-3 hours
    Resolution:                  |   Keywords:
Progress State:  in progress     |
---------------------------------+-------------------------------
Changes (by zzzeek):

 * priority:  medium => highest
 * severity:  no triage selected yet => major - 1-3 hours
 * status_field:  awaiting triage => in progress


Comment:

 (internal pdb notes follow)

 the turning point that is different in 0.9 is due to clause adaptation
 failing for raw joins, branch point is in orm/util.py, when joining for
 joinedload for second User.profile:

 {{{
         if prop:
             if sql_util.clause_is_present(on_selectable,
 left_info.selectable):
                 adapt_from = on_selectable
             else:
                 adapt_from = left_info.selectable
 }}}

 the clause_is_present() check fails and it the join doesn't have a
 specific enough "adapt_from".

 that check fails because onclause.comparator._source_selectable() does
 this: the mapped entity is:

 {{{
 > /Users/classic/dev/sqlalchemy/lib/sqlalchemy/orm/util.py(744)__init__()
 -> left_orm_info = getattr(left, '_joined_from_info', left_info)
 (Pdb) print
 onclause.comparator.property.parent._with_polymorphic_selectable
 party JOIN "user" ON party.party_id = "user".party_id
 (Pdb)
 }}}

 the _adapt_to_entity is:

 {{{
 (Pdb) print onclause.comparator._adapt_to_entity.selectable
 party AS party_1 JOIN "user" AS user_1 ON party_1.party_id =
 user_1.party_id
 }}}

 the adaptation in _source_selectable() fails, by taking the
 _adapt_to_entity and replacing it for both "party" and "user" in the
 mapped selectable, forming a garbage selectable:

 {{{
 (Pdb) print onclause.comparator._source_selectable()
 party AS party_1 JOIN "user" AS user_1 ON party_1.party_id =
 user_1.party_id JOIN party AS party_1 JOIN "user" AS user_1 ON
 party_1.party_id = user_1.party_id ON party_1.party_id = user_1.party_id
 }}}

 so the issue is ultimately with _source_selectable().

 so far a diff like this is working:

 {{{
 diff --git a/lib/sqlalchemy/orm/relationships.py
 b/lib/sqlalchemy/orm/relationships.py
 index 982f10a..6fdedd3 100644
 --- a/lib/sqlalchemy/orm/relationships.py
 +++ b/lib/sqlalchemy/orm/relationships.py
 @@ -747,11 +747,10 @@ class RelationshipProperty(StrategizedProperty):
              return self.property.parent

          def _source_selectable(self):
 -            elem = self.property.parent._with_polymorphic_selectable
 -            if self.adapter:
 -                return self.adapter(elem)
 +            if self._adapt_to_entity:
 +                return self._adapt_to_entity.selectable
              else:
 -                return elem
 +                return self.property.parent._with_polymorphic_selectable

          def __clause_element__(self):
              adapt_from = self._source_selectable()
 }}}

 but we can't test it fully because #2907 is breaking all the tests, so
 have to fix that first.

--
Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2908#comment:1>
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