Thank you! You are not an SQL alchemist, you are a SQL Wizard! Thank you
again!
For bonus points, an order by is possible on the discriminator like objects
are returned consecutively:
poly = with_polymorphic(
AddressAssociation,
[Customer.assoc_cls, Supplier.assoc_cls], aliased=True)
eager_addresses = session.query(Address).options(
joinedload(Address.association.of_type(poly)).joinedload(
poly.CustomerAddressAssociation.parent),
joinedload(Address.association.of_type(poly)).joinedload(
poly.SupplierAddressAssociation.parent),
).order_by(poly.discriminator.desc(), poly.id)
On Monday, November 24, 2014 4:04:41 PM UTC-8, Michael Bayer wrote:
>
>
> On Nov 24, 2014, at 5:16 PM, Michael Bayer <[email protected]
> <javascript:>> wrote:
>
>
> On Nov 24, 2014, at 12:31 PM, Michael Bayer <[email protected]
> <javascript:>> wrote:
>
>
> On Nov 24, 2014, at 1:00 AM, Victor Reichert <[email protected]
> <javascript:>> wrote:
>
> I've taken another look at trying to eager load the address.parent. Is it
> possible to do that?
>
>
> Unfortuntately not really. It should be in theory but I’m not able to
> work out an eager load that goes to both Customer and Supplier in terms of
> AddressAssociation at the same time. I can get the query to render just
> fine but the eager-targeting logic at the moment doesn’t seem to know how
> to be told to go to two separate subclasses of a base class at the same
> time. There’s probably improvements yet to be made in eager loading to
> support this case better, e.g. this is a bug, but I’ve wrestled with it for
> about an hour and I’m out of time on it for now, sorry. Even if it
> works, the query is very unpleasant to look at :) If I get it working
> later I’ll send it out.
>
>
> OK here we go, the limitation is that the of_type() modifier is only
> recognized along a particular path once. So to get over this we can use a
> with_polymorphic():
>
>
> good news, i whacked that limitation in the latest master for 1.0. so
> when 1.0 is released (in some months), you can do:
>
> eager_addresses = session.query(Address).options(
> joinedload(
> Address.association.of_type(Customer.assoc_cls)).joinedload(
> Customer.assoc_cls.parent),
> joinedload(
> Address.association.of_type(Supplier.assoc_cls)).joinedload(
> Supplier.assoc_cls.parent),
> )
>
> this will behind the scenes build up that with_polymorphic() thing for you.
>
>
>
>
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