select_limited_ids_list

# File activerecord/lib/active_record/associations.rb, line 1224
        def select_limited_ids_list(options, join_dependency)
          connection.select_all(
            construct_finder_sql_for_association_limiting(options, join_dependency),
            "#{name} Load IDs For Limited Eager Loading"
          ).collect { |row| connection.quote(row[primary_key]) }.join(", ")
        end