I recently shifted some of a database schema around, and thanks to
`association_proxy`, I've almost-eliminated the need to adjust my code
(thanks, Mike!).
I'm left with a situation on my caching layer that I can't seem to work
out. I can't seem to to find out the following information (or other
techniques that can help me figure out what I need)
1. what are the association_proxies on an object ?
2. have they been loaded ?
the use-case is this:
class Foo(base):
id = Column(Integer, primary_key=True)
bar = relationship(
"Bar",
primaryjoin="Foo.id==Bar.foo_id",
uselist=False,
)
bar_id = association_proxy("bar", "id")
* I have a `Foo` instance, that may or may not have eagerloaded `Bar` into
it.
* I only want to access `bar_id` if `Bar` has been loaded.
* I don't necessarily know that I have a `Foo` object or a `Bar`/`bar_id`
relation, as I am accessing this in a generic caching routing. I can
'hint' this information into the object if needed.
what I've tried/know:
* sqlalchemy.orm.class_mapper(Foo).mapped_table.c does not have `bar_id`
* sqlalchemy.orm.class_mapper(Foo).relationships does not have `bar_id`;
but it does have `bar`
* `fooInstance.__dict__` has a `bar` key when an eagerload happens
But i can't find a way to look at `fooInstance` and infer what the
association_proxies are.
My initial thought is to declare this stuff explicitly, but if there is a
way I could easily glean this information from the object, I think I may
prefer to do that.
does anyone have an idea?
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