funny joins

[Former user]

(original reporter: Justin) I have 2 tables:

 hosts : ip address (inet type)
 subnets: netmask   (cidr type)

I want to join the 2 tables, but the query needs to be something like

select * from hosts h, left join subnets s on h.ip << s.subnet;

right now I accomplish what I want to do with properties in the class:

class Subnet...:
    def _get_hosts(self):
        return Host.select(Host.c.ip._compare("<<", self.subnet))
    hosts = property(_get_hosts)

It only needs to be read only, as you don't do

h = Host.get(1)
s  = Subnet.get(2)
h.subnet = s

Instead, the .host and .subnet are pulled in based on what the address is.

[Former user]

(original author: anonymous) I do not understand the join condition "on h.ip << s.subnet". Could you give an example? For me, "a << b" shifts a from b bits to the left. Do you assume that the result is constrained to 32 bits?

[Mike Bayer]

sorry, have to put this on the back burner for awhile, unless someone wants to play with it. the recent refactorings in the property system should help.

[Former user]

(original author: ants) This has been possible for some time now.

mapper(Subnet, subnets, properties={
   'hosts': relation(Host,
       primaryjoin=hosts.c.ip.op('<<')(subnets.c.netmask),
       viewonly=True, foreign_keys=[hosts.c.ip](hosts.c.ip), uselist=True)})