Rails - Nov 2008 - Any progress on undirected self-referential many to many relationships?

I am going to re-ask a question that has been asked a few times in the
past. What is the best way to represent an undirected self-referential
many to many relationship. Trivial examples of this include an edge in
an undirected graph, or a mutual friendship.
Alice is a person
Bob is a person
Alice and Bob are friends of each other
We have a whole bunch of extra information about their friendship
(when it started, who introduced them, where they met, etc.)

We want to query "Are Bob and Alice friends?", "Who are
Bob''s
friends?", "Who are the people that introduce Bob to friends?"
etc.

We could represent this as a has_many :through relationship, with a
friendship_information database (containing extra information), and a
friendship database with two entries in the database per friendship
(<Bob, Alice> and <Alice, Bob>). But that seems inefficient.

Is there a better way to do this?

Alternatively, is there a way to merge 2 lists into a single has_many?
Like this:
  has_many :initiated_friendships, :foreign_key
=>''befriender_id'',
                                   :class_name =>
''Friendship'',
                                   :dependent => :destroy
  has_many :received_friendships,  :foreign_key
=>''befriendee_id'',
                                   :class_name =>
''Friendship'',
                                   :dependent => :destroy
  has_many :friends, :through=>union
(:received_friendships,:initiated_friendships)



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Bump!
-- 
Posted via http://www.ruby-forum.com/.

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Ewout Kleinsmann wrote:
> Bump!
Unbump! Just use the has_many :through option, and build the intermediate table 
by hand. There''s nothing "inefficient" about it; you just
have to keep tuning
the Model objects until they express your business rules, like any other model 
relationship...

-- 
   Phlip


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There is something inefficient about it. For it to act like an 
undirected graph the join table needs to have 2 rows per edge. AFAIK 
there is no good solution to this out there ... a "good" solution 
meaning one which doesn''t double the size of the join table to make the
directed graph behave like an undirected graph.

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