merge_outer_joins

# File activerecord/lib/active_record/relation/merger.rb, line 133
        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
            associations = other.left_outer_joins_values
            join_dependency = other.construct_join_dependency(
              associations, Arel::Nodes::OuterJoin
            )
            relation.joins!(join_dependency)
          end
        end