Rails - May 2008 - Eager loading of association extensions

Hello all,

Is it possible to do eager loading of association extensions?

That is, the following code produces one SQL query:

      cat = ProductCategory.find(:first, :include => :pricing_rules)
      cat.pricing_rules

But if in ProductCategory I have an association extension like this:

has_many :pricing_rules do
  def applicable()
    find(:all).select(&:applicable?)
  end
end

the code

        cat = ProductCategory.find(:first, :include => :pricing_rules)
        cat.pricing_rules.applicable

will produce 2 queries anyway, :include is useless here.

I see no other way that to add another association:

has_many :applicable_pricing_rules :conditions => ''appliccable is
true''

and then use it:

cat = ProductCategory.find(:first, :include => :applicable_pricing_rules)
cat.applicable_pricing_rules


But maybe there''s a way to eagerly load an association extension?


-- 
Best regards,
Yuri Leikind

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On May 8, 2:55 pm, "Yuri Leikind"
<yuri.leik...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> I see no other way that to add another association:
>
> has_many :applicable_pricing_rules :conditions => ''appliccable
is true''
>
> and then use it:
>
> cat = ProductCategory.find(:first, :include =>
:applicable_pricing_rules)
> cat.applicable_pricing_rules
>
> But maybe there''s a way to eagerly load an association extension?
There is no way. The extra association route would also be more
efficient because you only query the database for the relevant records
rather than getting all of them and then throwing away some.
But you could rewrite your association so that it uses pricing_rules,
ie

def applicable
  load_target.select(&:applicable?)
end

Fred
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