supply a pre-built comparator on associationproxy instead of requiring homegrown

[Former user]

Let's consider the example given in the documentation. One can do:

s.query(User).filter(User.user_keywords.contains(user_keyword))

but he can't do:

s.query(User).filter(User.keywords.contains(keyword))

because:

AttributeError: 'AssociationProxy' object has no attribute 'contains'

That's why, when I use the association_proxy pattern, I also add another view only relation between the two referenced objects (in this case User and Keyword), using the secondary table. I use this relation for selecting, and I use the association_proxy relation for inserting...

This duplication is annoying. I don't know if it's possible to solve the problem, but I want to be able to do:

s.query(User).filter(User.keywords.contains(keyword))

[e-mail]

[Former user]

submitted by [e-mail]

[Mike Bayer]

it is possible using a comparable_property mapping to your descriptor:

http://www.sqlalchemy.org/docs/05/reference/orm/mapping.html#sqlalchemy.orm.comparable_property

build a Comparator and implement the comparison methods you'd like and they will be assembled on your associationproxy.

im wondering how hard it would be to build this into associationproxy directly.

[Former user]

I wanted to use the has and any functions on associationproxies, and didn't know about about comparable_property, so I added this to AssociationProxy:

import sqlalchemy.exceptions as sa_exc

#snip

    def any(self, criterion=None, **kwargs):
        if self._target_is_scalar():
            raise sa_exc.InvalidRequestError("'any()' not implemented for scalar attributes. Use has().")
        return self._get_property().comparator.any(getattr(self.target_class, self.value_attr).has(criterion, **kwargs))

    def has(self, criterion=None, **kwargs):
        if not self._target_is_scalar():
            raise sa_exc.InvalidRequestError("'has()' not implemented for collections.  Use any().")
        return self._get_property().comparator.has(getattr(self.target_class, self.value_attr).has(criterion, **kwargs))

I'll try using a comparable_property instead now, but if it's possible to implement a general solution for AssociationProxy, I'd be willing to try to figure out the other Comparator functions.

[Former user]

Here's a patch against 26edef4f2483f68d6a527684a6d0aed37554534d that adds proxying of .any(), .has(), .contains(), ==, and != to association_proxies. Lots of tests are included.

Any thoughts on whether or not this implementation is appropriate?

Also, please add [e-mail] to the cc list on this ticket. Thanks!

[Former user]

(original author: ged)

[Mike Bayer]

hey this is a great patch. We just have to work the unittest to use MappedTest, Comparable and eq_ (at the very least speeds up the test to only setup/teardown once for the whole suite) and its good to go.

[Mike Bayer]

Scott, you are the man. this is in 2d15d9b0d0b20190d5aa348edaf4b398263464f7 thanks !

[Mike Bayer]

Removing milestone: 0.6.0 (automated comment)