merge_outer_joins

# File activerecord/lib/active_record/relation/merger.rb, line 135
        def merge_outer_joins
          return if other.left_outer_joins_values.blank?

          if other.klass == relation.klass
            relation.left_outer_joins!(*other.left_outer_joins_values)
          else
            joins_dependency = other.left_outer_joins_values.map do |join|
              case join
              when Hash, Symbol, Array
                ActiveRecord::Associations::JoinDependency.new(
                  other.klass, other.table, join
                )
              else
                join
              end
            end

            relation.left_outer_joins!(*joins_dependency)
          end
        end