Rails 4 Ransacker to build subquery for searching across multiple fields in multiple polymorphic classes.

any_controller.rb

#This is how it might be used. Create your instance which could be polymorphic or just a class.
#Search using the predicate 'in' because the subquery find_term will return an ID of every record that matches.
@profile_instance = either a PetProfile or an OwnerProfile
@profile_instance.search( { :find_term_in => "has fleas", :other_ransack_term_eq => "foobar" } ).results()

owner_profile.rb

class OwnerProfile < Profile

	ransacker :find_term, :formatter => proc {|val| OwnerProfile.find_term(val.downcase) }, :splat_param => true, :type => :string do
		arel_table[:id]
	end
	def self.find_term(val)
		my_arel = Arel::Table.new(OwnerProfile.table_name)
		my_arel.project(my_arel[:id])
		.where(Arel::Nodes::InfixOperation.new('LIKE', my_arel[:self_assessment].lower, "%#{val}%")
			.or(Arel::Nodes::InfixOperation.new('LIKE', my_arel[:friend_assessment].lower, "%#{val}%"))
		)
	end

end

pet_profile.rb

class PetProfile < Profile

	ransacker :find_term, :formatter => proc {|val| PetProfile.find_term(val.downcase) }, :splat_param => true, :type => :string do
		arel_table[:id]
	end
	def self.find_term(val)
		my_arel = Arel::Table.new(PetProfile.table_name)
		my_arel.project(my_arel[:id])
		.where(Arel::Nodes::InfixOperation.new('LIKE', my_arel[:owner_assessment].lower, "%#{val}%"))
	end

end

profile.rb

class Profile < ActiveRecord::Base
  #... anything you need for the parent class
end

You could also do this in a has_many type configuration where OwnerProfile has_many PetProfile.
In this case the query would look like
OwnerProfile.search({:find_term_or_pet_profiles_find_term_in => "has_fleas"}).result()