Searching across multiple associations that reference the same model/table joining on the wrong association

[jhdavids8]

Hi all!

Let's say I have a model such as:

class Recommendation < ActiveRecord::Base
  belongs_to :user
  belongs_to :target_user, class_name: 'User'
end

Now, say my Ransack search filters looks like this (as JSON, as I'm using Ransack with a REST API. Hopefully, it's more readable):

q: {
  user: {
    job_title: { 
      eq: "Designer"
    }
  },
  target_user: {
    group: {
      name: {
        eq: "Design"
      }
    }
  }
}

When I was on Rails 4.0.2 and Ransack 1.2.1, this was the SQL output I received:

"SELECT \"recommendations\".* FROM \"recommendations\" 
LEFT OUTER JOIN \"users\" ON \"users\".\"id\" = \"recommendations\".\"user_id\" 
LEFT OUTER JOIN \"users\" \"target_users_recommendations\" ON \"target_users_recommendations\".\"id\" = \"recommendations\".\"target_user_id\" 
LEFT OUTER JOIN \"groups\" ON \"groups\".\"id\" = \"target_users_recommendations\".\"department_id\" 
WHERE ((\"users\".\"job_title\" = 'Designer' AND \"groups\".\"name\" = 'Design'))"

Notice how the group is joined here (4th line, last LEFT OUTER JOIN).

However, after upgrading to Rails 4.1.1 and the Ransack 4.1 branch, this is the SQL output, which is wrong, as notice now how the group is joined (it's joined on the first user association, not the target user association).

"SELECT \"recommendations\".* FROM \"recommendations\"
LEFT OUTER JOIN \"users\" ON \"users\".\"id\" = \"recommendations\".\"user_id\" 
LEFT OUTER JOIN \"users\" \"target_users_recommendations\" ON \"target_users_recommendations\".\"id\" = \"recommendations\".\"target_user_id\" 
LEFT OUTER JOIN \"groups\" ON \"groups\".\"id\" = \"users\".\"department_id\" 
WHERE ((\"users\".\"job_title\" = 'Designer' AND \"groups\".\"name\" = 'Design'))"

This is consistent across several specs I have failing at the moment. Any query on an association for the second user association will fail, as it joins on the former user association.

Hopefully this is enough to get you guys started, but if not, please let me know. I'm going to try and find some time to dig deeper myself. Thanks!

[jonatack]

Hi @jhdavids8, thanks for the report. Just merged in a fix by @dush for a merged join issue on the rails-4.1 branch. I think it's a different issue, but could you give it a try and see if it helps?

[jhdavids8]

Unfortunately, it doesn't seem to have fixed the issue. I'm still seeing the same specs fail for the same reasons.

[arjes]

I'm getting hit with this issue too when upgrading to Rails 4.1

class User < ActiveRecord::Base
  has_many :comments
  has_many :foo, through: :comments
end
 class Comment < ActiveRecord::Base
  belongs_to :user
  has_many :foo
end
class Foo < ActiveRecord::Base
  belongs_to :comment
end

User.first.foo.search(:comment_user_name_eq => "omg").result.to_sql

This produces different code in 4.0 vs 4.1

Rails 4.1

SELECT "foos".* FROM "foos" 
LEFT OUTER JOIN "comments" "comments_foos" ON "comments_foos"."id" = "foos"."comment_id" 
LEFT OUTER JOIN "users" ON "users"."id" = "comments"."user_id" 
INNER JOIN "comments" ON "foos"."comment_id" = "comments"."id" 
WHERE "comments"."user_id" = ? AND "users"."name" = 'omg'

Rails 4.0

SELECT "foos".* FROM "foos" 
LEFT OUTER JOIN "comments" "comments_foos" ON "comments_foos"."id" = "foos"."comment_id" 
LEFT OUTER JOIN "users" ON "users"."id" = "comments_foos"."user_id" 
INNER JOIN "comments" ON "foos"."comment_id" = "comments"."id" 
WHERE "comments"."user_id" = ? AND "users"."name" = 'omg'

Note that the differences is in this line

LEFT OUTER JOIN "users" ON "users"."id" = "comments"."user_id"

This happens on Master and Rails 4.1. Here is a repo with the code I used to create the above:
https://github.com/arjes/ransack-rails4.1-join-on-bug

If you can point me in the right direction I can try to help, when I'm not working.

[jonatack]

It's likely to be in Ransack::Adapters::ActiveRecord:Context. Or possibly Ransack::Context.

@huoxito wdyt?

[huoxito]

My initial guess is Ransack::Context#build_for_find_association. It's hard to tell for sure without further investigation though. It might as well as be something wrong in rails. Looking into it. I think we could also try to improve that same method to use more of activerecord public api. Chances are we'd have a more reliable implementation.

@arjes @jhdavids8 any chance you guys could give us a spec that would fail on 4.1 but pass on 4.0? That should help a lot to fix the issue and ensure it doesn't happen again.

[jonatack]

@huoxito yes, my initial guess would be in that method.

[jhdavids8]

Hi @huoxito I'm looking into this now. Stay tuned!

[jhdavids8]

Well, this is a pretty poor effort at a spec that fails on 4.1 but not on 4.0, but here it is.

I did as much digging as time allowed, but my lack of knowledge on the inner workings of ActiveRecord and Polyamorous prevented me from getting too far. The error definitely appears to be in Ransack::Context#build_for_find_association though. Everything appeared normal up to line 177, where the JoinDependency is built. That dependency appeared to have nothing that linked it to the aliased association (in my code, this was :target_person) over the non-aliased one (just :person).

Sorry, but that's as far as I could get for now. If you guys don't beat me to a solution, I'll try to find some more time to dig deeper later in the week. Thanks!

[huoxito]

Thank you @jhdavids8! I'll take a look again and try out the spec as soon as I get some spare time, let you know if I find any solution

[avit]

It looks like the 4.1 conditional branch builds a new JoinDependency, but the "else" branch uses the assigned @join_dependency instance variable. That's a likely clue here.

[JanStevens]

Any update on this issue? I have the exact same issue where ransack fails to find the renamed column and thus generates a postgres error.

[jonatack]

Thanks for the heads up. If there was an update I would try to make sure it was referenced here and visible. Anyone who is affected by this issue is most welcome to work on a fix.

[clammers]

Issue also occured in rails 4.2 with ransack 1.5.1. Fix would be great!

[yairlev]

Same issue with rails 4.1.0 and ransack 1.6.2

[sitch]

Same issue with rails 4.1.8 and ransack 1.6.4, 4.1 branch, and current master branch