ON

# File activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb, line 336
                                  def          ONONONONON (adrelid = attrelid AND adnum = attnum)
              JOIN pg_constraint  cons ON (conrelid = adrelid AND adnum = conkey[1])
              JOIN pg_namespace   nsp  ON (t.relnamespace = nsp.oid)
              WHERE t.oid = #{quote(quote_table_name(table))}::regclass
                AND cons.contype = 'p'
                AND pg_get_expr(def.adbin, def.adrelid) ~* 'nextval|uuid_generate'
            SQL
          end

          pk = result.shift
          if result.last
            [pk, PostgreSQL::Name.new(*result)]
          else
            [pk, nil]
          end
        rescue
          nil
        end