Re: [SQLObject] Thoughts on joins...

[Robin M. <rob...@gm...>]

On 10/11/05, Luke Opperman <lu...@me...> wrote:
> I'll agree on MultipleJoin, although the one nice thing would be if in th=
e
> default case it was automatically created, or at least the opposing colum=
n
> name was auto - in which case the explicit MultipleJoin is just for alter=
nate
> naming and resolving the case of multiple FKs to the same class. But we'r=
e not
> doing that now, so no difference from the manual select.

I don't think we'd need MultipleJoin even in the case of resolving
multiple FKs to the same class, if give ForeignKey a parameter to
specify the name of the auto-created attribute in the other class.
Something like this:


class Factory(SQLObject):
    location =3D StringCol()

class Widget(SQLObject):
    barcode =3D StringCol()
    produced_in =3D ForeignKey("Factory", related_name=3D"widgets_produced"=
)
    shipped_to =3D ForeignKey("Factory", related_name=3D"widgets_received")

acme =3D Factory(location=3D"ACME Corp. Headquarters")
foo =3D Factory(location=3D"Foo, Inc. Manufacturing")
widget1 =3D Widget(barcode=3D"123", produced_in=3Dacme, shipped_to=3Dfoo)
widget2 =3D Widget(barcode=3D"456", produced_in=3Dfoo, shipped_to=3Dacme)

print list(acme.widgets_produced)  # prints [<Widget 1 barcode=3D"123" ...>=
]
print list(foo.widgets_received)  # prints [<Widget 1 barcode=3D"123" ...>]
print list(foo.widgets_produced)  # prints [<Widget 2 barcode=3D"456" ...>]
print list(acme.widgets_received)  # prints [<Widget 2 barcode=3D"456" ...>=
]


Factory.widgets_produced and Factory.widgets_received could still be
automatically-created MultipleJoins like we have now, but I think I'd
also rather see them as auto-created select() calls, as Ian suggested
_get_foos() should be in his original email of the thread.

I'm not entirely sure about "related_name" as the name of the keyword
argument. That's what Django uses, because they refer to ForeignKeys
as "Relations". Another name might be better for the terminology
SQLObject uses.

Thoughts?

--
Robin Munn
Rob...@gm...
GPG key 0xD6497014