Rails core - Jan 2011 - Should includes with general association name work?

Hi, I''m wondering if this is an arel bug or should be a new feature.

I''ve got a model with the following:

     has_many :recommendations,  :class_name => "Referral",
:foreign_key => :candidate_id
    scope :recommended_to, lambda {|er|
joins(:recommendations).where(:referrals => {:employer_representative
=> er})}

This works and generates the right inner join.

puts User.recommended_to(er).to_sql
users" INNER JOIN "referrals" ON
"referrals"."candidate_id" "users"."id"
WHERE ("referrals"."employer_representative" =
''6'')

But if I change joins to includes in the scope, I get:
puts User.recommended_to(er).to_sql
SELECT "users".* FROM "users" WHERE
("referrals"."employer_representative" =
''6'')

Which won''t work since it needs the join.

I know that the old :include option only generated a join clause if
there was also a condition which required it, and since the includes
method doesn''t know that it kind of makes sense.  I also tried
chaining the includes after the where in hopes that then include WOULD
know, but it didn''t make a difference.

Is there, or should there, be a way in such a case to force includes
to generate the join as well as instantiating the associated records?


-- 
Rick DeNatale

Blog: http://talklikeaduck.denhaven2.com/
Github: http://github.com/rubyredrick
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This looks like a bug to me. You should try a few things:

* Can you repro on master?
* What about doing where(''referrals.employer_representative''
=> ...) -
does that make a difference?
* Try doing the query manually (i.e. Users.includes(..).where(...)) - I
doubt the scope is the problem but good to rule things out.

(BTW the bug is probably in ActiveRecord::Relation, not arel. Also,
specifying the query in a different order won''t make a difference since
the query will only be built when it''s needed, not incrementally.)

Cheers

On Tue, 2011-01-11 at 12:05 -0500, Rick DeNatale wrote:
> Hi, I''m wondering if this is an arel bug or should be a new
feature.
> 
> I''ve got a model with the following:
> 
>      has_many :recommendations,  :class_name => "Referral",
> :foreign_key => :candidate_id
>     scope :recommended_to, lambda {|er|
> joins(:recommendations).where(:referrals => {:employer_representative
> => er})}
> 
> This works and generates the right inner join.
> 
> puts User.recommended_to(er).to_sql
> users" INNER JOIN "referrals" ON
"referrals"."candidate_id" >
"users"."id" WHERE
("referrals"."employer_representative" =
''6'')
> 
> But if I change joins to includes in the scope, I get:
> puts User.recommended_to(er).to_sql
> SELECT "users".* FROM "users" WHERE
> ("referrals"."employer_representative" =
''6'')
> 
> Which won''t work since it needs the join.
> 
> I know that the old :include option only generated a join clause if
> there was also a condition which required it, and since the includes
> method doesn''t know that it kind of makes sense.  I also tried
> chaining the includes after the where in hopes that then include WOULD
> know, but it didn''t make a difference.
> 
> Is there, or should there, be a way in such a case to force includes
> to generate the join as well as instantiating the associated records?
> 
> 
> -- 
> Rick DeNatale
> 
> Blog: http://talklikeaduck.denhaven2.com/
> Github: http://github.com/rubyredrick
> Twitter: @RickDeNatale
> WWR: http://www.workingwithrails.com/person/9021-rick-denatale
> LinkedIn: http://www.linkedin.com/in/rickdenatale
> 
-- 
http://jonathanleighton.com/