This is a perfectly usable solution. Thanks so much!
On Wednesday, September 16, 2015 at 11:39:57 AM UTC-7, Michael Bayer wrote:
>
> OK, new day, new perspectives. This is the best way to do the mapping /
> type:
>
> class CastToIntegerType(TypeDecorator):
> impl = String
>
> def column_expression(self, col):
> return cast(col, Integer)
>
> def process_bind_param(self, value, dialect):
> return str(value)
>
>
> class Person(Base):
> __tablename__ = 'person'
> id = Column('id_string', CastToIntegerType, primary_key=True)
>
> pets = relationship(
> 'Pets',
> primaryjoin='foreign(Pets.person_id)==cast(Person.id, Integer)')
>
>
>
> we keep the Python conversion of int to string in Python, then cast in
> the primaryjoin. That way lazyload gives us:
>
> SELECT pets.id AS pets_id, pets.person_id AS pets_person_id
> FROM pets
> WHERE pets.person_id = CAST(%(param_1)s AS INTEGER)
> 2015-09-16 14:37:00,449 INFO sqlalchemy.engine.base.Engine {'param_1':
> '5'}
>
> joinedload gives us:
>
> SELECT CAST(anon_1.person_id_string AS INTEGER) AS
> anon_1_person_id_string, pets_1.id AS pets_1_id, pets_1.person_id AS
> pets_1_person_id
> FROM (SELECT person.id_string AS person_id_string
> FROM person
> LIMIT %(param_1)s) AS anon_1 LEFT OUTER JOIN pets AS pets_1 ON
> pets_1.person_id = CAST(anon_1.person_id_string AS INTEGER)
>
>
> so no double cast, and also the fact that we have string coersion still
> happening in the lazyload is appropriate, as the type converters take
> place the same way as they would in the joined load.
>
>
>
>
>
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