[Dbix-class] How to setup a complicated (bilateral) relationship?

[Steve Francia]

Matt S Trout wrote:
> On Fri, Jun 22, 2007 at 01:09:15PM -0400, Steve Francia wrote:
>   =

>> I have a rather complicated relationship that I am struggling with
>> setting up, hopefully I can explain it so it makes sense. I will also
>> include what we have thus far.
>>
>> I have two tables user and friends, friends is a join table that joins
>> users to users. In my system, friendship is bilateral, meaning to have a
>> friend is to be one.
>> I worked through the reciprocal relationship alright, but the bilateral
>> part has me stumped.
>>     =

>
> You can use an OR in the join cond, although it's not always as efficient
> on MySQL as you might like -
>
> has_many(friend_link =3D> ...::Friend =3D> [
>            { 'foreign.f1_id' =3D> 'self.id' },
>            { 'foreign.f2_id' =3D> 'self.id' },
>          ]);
>
> which will do
>
> user me JOIN friend friend_link
> ON (friend_link.f1_id =3D me.id OR friend_link.f2_id =3D me.id)
>
>   =

Thanks Matt,
This is nearly there, certainly a lot closer than I had on my own.. But
it isn't quite right.
The way this is currently it joins half the relationships back to the
original user, so $user->friend is the $user itself.
I believe this is because the relationship is only setup on one of the
keys, even though we use both for the join.
Perhaps this cannot be accomplished with one relationship, and two are
needed? friends, and myfriends and we will join them outside of the model?
-Steve

BTW there are various reasons why we are not using two rows. 1. being,
it is messier from a database point of view. 2. We always want bilateral
relationships, and never unilateral ones (I am your friend, but you are
not mine). 3. It is more maintainable. 4. It is more scalable when
dealing with large number of rows..

-- =

Steve Francia
Lead Developer
Takkle, Inc.
212.792.5859 (fax)
steve at takkle.com

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