Rails search with OR in ActiveRecord::Relation

After a very long search I'm finally asking this question: How do I do OR condition queries with ActiveRecord::Relation in Rails 3.0? Basically I believe it has to do something with scoping and stuff....

Here is what I have:

class Practice < ActiveRecord::Base
  attr_accessible :name

  has_and_belongs_to_many :doctors
  has_and_belongs_to_many :services
end

class Doctor < ActiveRecord::Base
  attr_accessible :first_name, :last_name

  has_and_belongs_to_many :practices
  has_and_belongs_to_many :services
end

class Service < ActiveRecord::Base
  attr_accessible :name, :about

  has_and_belongs_to_many :practices
  has_and_belongs_to_many :doctors
end

What I want to achieve is a form where I can do a search queries and get back ActiveRecord::Relation object(so I can use it with will_paginate and so on) with list of Practices. The query should find any Practice where @practice.name matches query_string OR where @practice.doctors.first_names matches query_string OR where @practice.doctors.last_names matches query_string OR @practice.services.names matches query_string. In other words - lets say query_string matches name of a Service the I would like to get back list of Practices related to this Service. Or if first_name or last_name of a Doctor matches query_string then I get Practices associated to this Doctor/Doctors. And of course good old match by Practice.name too :D

I realize that my has_and_belongs_to_many associations aren't good here, it's just for demonstration purpose but I would be happy to hear if someone can help with migrations and associations for my case.

Thanks.

P.S. as I s开发者_JS百科aid I use Rails 3.0 and I believe it has to do something about scopes(but I can be wrong of course). Also I've tried MetaWhere but couldn't make it work.... :(

---

Let's see how this turns out:

class Practice < ActiveRecord::Base
  class < self
    def by_any_name(param)
      joins(:doctors, :services).
      where(<<-SQL, :name => param)
             doctors.first_name = :name OR
             doctors.last_name  = :name OR
             practices.name     = :name OR
             services.name      = :name
      SQL
    end
  end
end

Scopes are so last-year.

And some left joins fer ya (needs testing!):

joins('LEFT JOIN
         (doctors_practices INNER JOIN doctors
            ON doctors.id = doctors_practices.doctors_id)
          ON doctors_practices.practice_id = practices.id
       LEFT JOIN
         (practices_services INNER JOIN services
            ON services.id = practices_services.service_id)
          ON practices_services.practice_id = practices.id')

Sheesh, way past my bedtime.

---

You can dig into ARel OR --see what I did there :)-- check out the very handy gem squeel, which lets you do exactly what you want with a nice syntax.

https://github.com/ernie/squeel