build_joins

# File activerecord/lib/active_record/relation/query_methods.rb, line 1103
      def build_joins(manager, joins, aliases)
        buckets = Hash.new { |h, k| h[k] = [] }

        unless left_outer_joins_values.empty?
          left_joins = valid_association_list(left_outer_joins_values.flatten)
          buckets[:stashed_join] << construct_join_dependency(left_joins, Arel::Nodes::OuterJoin)
        end

        joins.map! do |join|
          if join.is_a?(String)
            table.create_string_join(Arel.sql(join.strip)) unless join.blank?
          else
            join
          end
        end.delete_if(&:blank?).uniq!

        while joins.first.is_a?(Arel::Nodes::Join)
          join_node = joins.shift
          if join_node.is_a?(Arel::Nodes::StringJoin) && !buckets[:stashed_join].empty?
            buckets[:join_node] << join_node
          else
            buckets[:leading_join] << join_node
          end
        end

        joins.each do |join|
          case join
          when Hash, Symbol, Array
            buckets[:association_join] << join
          when ActiveRecord::Associations::JoinDependency
            buckets[:stashed_join] << join
          when Arel::Nodes::Join
            buckets[:join_node] << join
          else
            raise "unknown class: %s" % join.class.name
          end
        end

        build_join_query(manager, buckets, Arel::Nodes::InnerJoin, aliases)
      end