I see, thank you, Mike.
So, looks like I just wanted strange thing: having class to be distinct
from itself.
Thank you for clarifying!
Dmytro
вт, 25 черв. 2019 о 19:26 Mike Bayer <mike...@zzzcomputing.com> пише:
>
>
> On Fri, Jun 21, 2019, at 7:22 AM, Dmytro Starosud wrote:
>
> Base class A1 contains polymorphic_identity (along with polymorphic_on),
> but Query(A1)doesn't produce where clause, whereas Query(A2) (where A2 is
> subclass of A1 with its own polymorphic_identity) does.
>
> Tried looking in docs with no success. I think I am just missing something.
>
> from sqlalchemy import Column, Integer, Stringfrom sqlalchemy.ext.declarative
> import declarative_basefrom sqlalchemy.orm import Query, configure_mappers
> Base = declarative_base()
>
> class A1(Base):
> __tablename__ = 'a1'
> id = Column(Integer, primary_key=True)
> poly_on = Column(String, nullable=False)
> __mapper_args__ = {
> 'polymorphic_on': poly_on,
> 'polymorphic_identity': 'a1',
> }
>
> class A2(A1):
> __mapper_args__ = {
> 'polymorphic_identity': 'a2',
> }
>
>
> configure_mappers()
> print(Query(A1))# SELECT a1.id AS a1_id, a1.poly_on AS a1_poly_on# FROM a1
> print(Query(A2))# SELECT a1.id AS a1_id, a1.poly_on AS a1_poly_on# FROM a1#
> WHERE a1.poly_on IN (:poly_on_1)
>
> I would expect WHERE clauses in both cases.
>
>
>
> what would the first WHERE clause be limiting on ?
>
> an A2 is an A1, so if you are querying for all A1 objects, you should get
> those that are A2 as well.
>
> if you want to affect how this works you can use the before_compile event
> to add whatever filters you'd like, see the example at
> https://github.com/sqlalchemy/sqlalchemy/wiki/FilteredQuery
>
>
>
> Originally posted here <https://stackoverflow.com/q/56701668/3151829>.
>
>
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