instance method custom_join_sql

# File activerecord/lib/active_record/relation/query_methods.rb, line 152
    def custom_join_sql(*joins)
      arel = table.select_manager

      joins.each do |join|
        next if join.blank?

        @implicit_readonly = true

        case join
        when Array
          join = Arel.sql(join.join(' ')) if array_of_strings?(join)
        when String
          join = Arel.sql(join)
        end

        arel.join(join)
      end

      arel.join_sql
    end