Rails - Apr 2006 - Primary keys and migrations

I have a join table I''m creating with a migration as follows:

     create_table :read_global_messages, :id=>false do |t|
       t.column :user_id, :integer
       t.column :message_id, :integer
     end

So far so good, however I want the primary key to be user_id and 
message_id. How do I do this?

I tried the following, but that doesn''t work:

     add_index :read_global_messages, [:user_id, :message_id], :primary

I could just add it as a normal index, but ideally I''d like it to be a 
primary key otherwise this table will be without one (as there''s no ID 
column).

Any ideas?

Thanks in advance.

-- 
R.Livsey
http://livsey.org

Richard Livsey wrote:
> I have a join table I''m creating with a migration as follows:
> 
>      create_table :read_global_messages, :id=>false do |t|
>        t.column :user_id, :integer
>        t.column :message_id, :integer
>      end
> 
> So far so good, however I want the primary key to be user_id and
> message_id. How do I do this?
Rails doesn''t support either composite primary keys or primary keys on 
join tables. If you need a primary key in your table, you probably want 
to make it a full-fledged join model (has_many :through instead of 
habtm).

--
Josh Susser
http://blog.hasmanythrough.com

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