[Sqlalchemy-tickets] [sqlalchemy] #2797: expression-level many-to-one comparison

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

#2797: expression-level many-to-one comparison
-------------------------+---------------------------------------
 Reporter:  zzzeek       |           Owner:  zzzeek
     Type:  enhancement  |          Status:  new
 Priority:  medium       |       Milestone:  0.9.0
Component:  orm          |        Severity:  minor - half an hour
 Keywords:               |  Progress State:  in queue
-------------------------+---------------------------------------
 Just as `obj.many_to_one == some_object` works, it should do the right
 thing if you say `obj.many_to_one == SomeClass`, which is actually
 longhand notation for the "primaryjoin" but is consistent in other
 systems.

 this is in 0.9 so it gets noticed but should be OK for a backport to 0.8.

 {{{
 #!python
 from sqlalchemy import *
 from sqlalchemy.orm import *
 from sqlalchemy.ext.declarative import declarative_base

 Base = declarative_base()

 class A(Base):
     __tablename__ = 'a'

     id = Column(Integer, primary_key=True)


 class B(Base):
     __tablename__ = 'b'

     id = Column(Integer, primary_key=True)
     a_id = Column(Integer, ForeignKey('a.id'))
     a = relationship("A")

 s = Session()

 # support this
 # q1 = s.query(B).filter(B.a == A).exists()

 # checks the argument, then just does this:
 q1 = s.query(B).filter(B.a.expression).exists()

 print s.query(A).filter(q1)
 }}}

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Ticket URL: <http://www.sqlalchemy.org/trac/ticket/2797>
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