On Thu, Apr 23, 2009 at 9:16 AM, kscaldef <kevin.scaldefe...@gmail.com> wrote:
>
> I had a closely related question today, which was why this code does N
> +1 queries?
>
> order.order_items.each {|oi| oi.order}
>
> Why must each order item do a query to find its order? It seems like
> Rails should recognize the reciprocal nature of the associations.
Yes, this is called bi-directional associations and would be a
welcome (if non-trivial) addition in 3.0.
Incidentally it actually only does 1 query, the rest are cache hits,
so at least your database is safe. However it still wastes memory and
can lead to some weirdness and should be fixed.
The has_many :foos, belongs_to :bar case is very easy, but there are
some common corner cases which we'll have to look at. For example
what's the inverse of belongs_to :bar when we have the following
associations to choose from:
has_many :foos, :conditions=>...
has_many :something_else, :class_name=>"Foo"
has_many :important_foos, :through=>...
Ideally we'd just punt on those cases and require users to explicitly
mark associations as inverses with a declaration like
has_many :foos, :conditions ... :inverse_of=>:bar
--
Cheers
Koz
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