anchor.diff:  handle_call(_Request, _From, State) ->
       {reply, ok, State}.
   
  +handle_cast(regist_schema,
  +            State = #?STATE{ conn_pid = Conn, database = DB }) ->
  +    {ok, #{<<"tables">> := Tables}} = eovsdb_protocol:get_schema(Conn, DB),
  +    {noreply, State#?STATE{ schema = Tables}};
  +handle_cast({regist_schema, DB},
  +            State = #?STATE{ conn_pid = Conn }) ->
  +    {ok, #{<<"tables">> := Tables}} = eovsdb_protocol:get_schema(Conn, DB),
  +    {noreply, State#?STATE{ schema = Tables}};
   handle_cast(connect, State = #?STATE{ ipaddr = Host,
                                         port = Port,
                                         connection_timeout = TimeOut}) ->
  
positive.code:          list_dbs/1,
           get_schema/1,
           get_schema/2,
           get_columns/2,
           transaction/2,
           transaction/3,
  
negative.code: 
  retry_connect(Pid, WaitTime) ->
      timer:apply_after(WaitTime, ?MODULE, signal_connect, [Pid]).
  
  table_schema(TabName, ColName, Schema)
    when is_atom(TabName),
         is_atom(ColName) ->
      TabNameBin = atom_to_binary(TabName, utf8),
      ColNameBin = atom_to_binary(ColName, utf8),
      table_schema(TabNameBin, ColNameBin, Schema);
  table_schema(TabName, ColName, Schema) ->
      case maps:get(TabName, Schema, false) of
          false -> {error, {TabName, not_found}};
          #{<<"columns">> := Columns} ->
              case maps:get(ColName, Columns, false) of
                  false ->
                      {error, {ColName, not_found}};
                  #{<<"type">> := Type} ->
                      column_schema(Type)
              end
      end.
  
  column_schema(#{<<"key">> := #{<<"enum">> := [<<"set">>, Enum]}}) ->
      {enum, Enum};
  column_schema(#{<<"key">> := #{<<"key">> := _, <<"value">> := _}}) ->
      map;
  column_schema(#{<<"key">> := #{<<"refTable">> := Table, <<"min">> := _}}) ->
      {set, {ref_table, Table}};
  column_schema(#{<<"key">> := #{<<"min">> := _, <<"type">> := Type}}) ->
      {set, Type};
  column_schema(#{<<"key">> := #{<<"refTable">> := Table}}) ->
      {ref_table, Table};
  column_schema(#{<<"key">> := Type}) ->
      Type;
  column_schema(Type) ->
      Type.
  