Rails - Jul 2005 - "has_many :finder_sql" vs iterating over has_many relationship

Hi,

Wondering which is more efficient / RoR preferred:

class Foo < ActiveRecord::Base
   has_many :bars

   def active_bars
     bars.inject([]) { |active,bar| active << bar if bar.active? }
   end
end

Or:

class Foo < ActiveRecord::Base
   has_many :bars
   has_many :active_bars,
            :class => ''Bar'',
            :finder_sql => "select * from bars where f_id=#{id} and 
active=1"
end

Hopefully I got the syntax on that second one right!  Essentially, in 
everyones opinion, is it better to iterate over an existing
''has_many''
relationship to find instances that are ''active'', or is it
better to
define another attribute where the result can be found from an SQL query?

I was writing the iteration technique, but then it occurred to me I 
could achieve it with the finder_sql (incurring an extra DB query, but 
not repeating the iteration on every call).

Matt

On 7/23/05, Matthew Denner
<matt-rdkfGonbjUS6Ep1eQ8kGe/TXAc8U3UkmXqFh9Ls21Oc@public.gmane.org>
wrote:
> Hi,
> 
> Wondering which is more efficient / RoR preferred:
> 
> class Foo < ActiveRecord::Base
>    has_many :bars
> 
>    def active_bars
>      bars.inject([]) { |active,bar| active << bar if bar.active? }
>    end
> end
> 
> Or:
> 
> class Foo < ActiveRecord::Base
>    has_many :bars
>    has_many :active_bars,
>             :class => ''Bar'',
>             :finder_sql => "select * from bars where f_id=#{id} and
> active=1"
> end
How about both:

class Foo < ActiveRecord::Base
  has_many :bars
  def active_bars
     bars.find(:all, :conditions=>"active=1")
  end
end
> Hopefully I got the syntax on that second one right!  Essentially, in
> everyones opinion, is it better to iterate over an existing
''has_many''
> relationship to find instances that are ''active'', or is
it better to
> define another attribute where the result can be found from an SQL query?
> 
> I was writing the iteration technique, but then it occurred to me I
> could achieve it with the finder_sql (incurring an extra DB query, but
> not repeating the iteration on every call).
> 
> Matt
> _______________________________________________
> Rails mailing list
> Rails-1W37MKcQCpIf0INCOvqR/iCwEArCW2h5@public.gmane.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
> 

-- 
Cheers

Koz