Rails - Jul 2006 - HowTo?: Eager caching of third order ActiveRecord assoc.

Hello.

Using the ":include", which generates a "LEFT OUTER JOIN"
SQL command,
it is possible to eagerly preload second order data objects (children)
for a given association.

I wanted to know, if it is possible to eagerly preload and cache
third order (or more) data objects, which are little-children or
little-little-children. As I''ve seen. it is possible to add
"LEFT OUTER JOIN" SQL clauses with the needed conditions,
to fetch little-little-children data, but how to do this with
ActiveRecord and its cache?

My models are as follow:

  # Model Software
  # -----------------------------
  class Software < ActiveRecord::Base
    has_many :releases, :exclusively_dependent => true
  end

  # Model Release
  # -----------------------------
  class Release < ActiveRecord::Base
    belongs_to :software
    has_many :acquisitions, :exclusively_dependent => true
  end

  # Model Acquisition
  # -----------------------------
  class Acquisition < ActiveRecord::Base
    belongs_to :release
    has_and_belongs_to_many :languages
  end

  # Model Language
  # -----------------------------
  class Language < ActiveRecord::Base
    has_and_belongs_to_many :acquisitions
  end

Is it possible to find(), or paginate() Software-s, while
eagerly preloading in cache their Release-s, the release
Acquisition-s, and the supported Language-s for those releases?
And how to do it?

Thank to all for your suggestions.



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On Monday, July 24, 2006, at 2:50 PM, Krassimir Todorov
wrote:
>Hello.
>
>Using the ":include", which generates a "LEFT OUTER
JOIN" SQL command,
>it is possible to eagerly preload second order data objects (children)
>for a given association.
>
>I wanted to know, if it is possible to eagerly preload and cache
>third order (or more) data objects, which are little-children or
>little-little-children. As I''ve seen. it is possible to add
>"LEFT OUTER JOIN" SQL clauses with the needed conditions,
>to fetch little-little-children data, but how to do this with
>ActiveRecord and its cache?
>
>My models are as follow:
>
>  # Model Software
>  # -----------------------------
>  class Software < ActiveRecord::Base
>    has_many :releases, :exclusively_dependent => true
>  end
>
>  # Model Release
>  # -----------------------------
>  class Release < ActiveRecord::Base
>    belongs_to :software
>    has_many :acquisitions, :exclusively_dependent => true
>  end
>
>  # Model Acquisition
>  # -----------------------------
>  class Acquisition < ActiveRecord::Base
>    belongs_to :release
>    has_and_belongs_to_many :languages
>  end
>
>  # Model Language
>  # -----------------------------
>  class Language < ActiveRecord::Base
>    has_and_belongs_to_many :acquisitions
>  end
>
>Is it possible to find(), or paginate() Software-s, while
>eagerly preloading in cache their Release-s, the release
>Acquisition-s, and the supported Language-s for those releases?
>And how to do it?
>
>Thank to all for your suggestions.
>
>
>
>--
>Posted via http://www.ruby-forum.com/.
>_______________________________________________
>Rails mailing list
>Rails@lists.rubyonrails.org
>http://lists.rubyonrails.org/mailman/listinfo/rails
Try this..

Software.find(:all, :include=>{:releases=>{:aquisitions=>:languages}})

In theory this should work, but YMMV.

_Kevin
www.sciwerks.com

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Kevin Olbrich wrote:
> On Monday, July 24, 2006, at 2:50 PM, Krassimir Todorov wrote:
>>to fetch little-little-children data, but how to do this with
>>  # Model Release
>>    has_and_belongs_to_many :languages
>>Acquisition-s, and the supported Language-s for those releases?
>>Rails@lists.rubyonrails.org
>>http://lists.rubyonrails.org/mailman/listinfo/rails
> 
> Try this..
> 
> Software.find(:all,
:include=>{:releases=>{:aquisitions=>:languages}})
> 
> In theory this should work, but YMMV.
> 
> _Kevin
> www.sciwerks.com
GREAT ... IT WORKS ...

Thank you very much!

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The result is OK, and retreived data is really cached.

Thank you again, Kevin!


Krassimir Todorov wrote:
> Kevin Olbrich wrote:
>> On Monday, July 24, 2006, at 2:50 PM, Krassimir Todorov wrote:
>>>to fetch little-little-children data, but how to do this with
>>>  # Model Release
>>>    has_and_belongs_to_many :languages
>>>Acquisition-s, and the supported Language-s for those releases?
>>>Rails@lists.rubyonrails.org
>>>http://lists.rubyonrails.org/mailman/listinfo/rails
>> 
>> Try this..
>> 
>> Software.find(:all,
:include=>{:releases=>{:aquisitions=>:languages}})
>> 
>> In theory this should work, but YMMV.
>> 
>> _Kevin
>> www.sciwerks.com
> 
> GREAT ... IT WORKS ...
> 
> Thank you very much!

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