class Magazine < ActiveRecord::Base
  belongs_to :publisher, foreign_key: :publisher_id
  has_many :issues
end
class Issue < ActiveRecord::Base
  belongs_to :magazine
end
class Publisher < Client
  has_many :magazines, foreign_key: :publisher_id
  has_many :issues, through: :magazines
end
class Client < ActiveRecord::Base
end

publishers_table = Publisher.arel_table
magazines_table = Magazine.arel_table
publisher_join = magazines_table.join(publishers_table, Arel::Nodes::OuterJoin).
    on(publishers_table[:id].eq(magazines_table[:publisher_id])).join_sources

Issue.eager_load(:magazine).joins(publisher_join).where(publishers_table[:name].eq('my publisher'))