anchor.diff:                      , status    ::atom()            %% undefined | waiting | fetching | done | tailing | aborted
                       , metarec   ::tuple()
                       , blockSize=100 ::integer()     %% could be adaptive
  -                    , remaining ::integer()         %% rows remaining to be fetched. initialized to Limit and decremented
  +                    , remaining=0   ::integer()         %% rows remaining to be fetched. initialized to Limit and decremented
                       , opts = [] ::list()            %% fetch options like {tail_mode,true}
                       , tailSpec  ::any()             %% compiled matchspec for master table condition (bound with MetaRec) 
                       , filter    ::any()             %% filter specification {Guard,Binds}
  
positive.code:     Result = gen_server:call(Pid, {update_cursor_execute, IsSec, SKey, optimistic}),
      % ?Log("update_cursor_execute ~p~n", [Result]),
      case Result of
          KeyUpd when is_list(KeyUpd) -> KeyUpd;
          Error ->    throw(Error)
      end.
  
  close(SKey, #stmtResult{stmtRef=Pid}) ->
  
negative.code:             imem_meta:log_to_db(error,?MODULE,handle_call,[{reason,Reason},{updPlan,UpdatePlan}],"update_cursor_execute error"),
              {error,Reason}
      end,
      ?Log("update_cursor_execute result ~p~n", [Reply]),
      FetchCtx1 = FetchCtx0#fetchCtx{monref=undefined, status=aborted},   %% , metarec=undefined
      {reply, Reply, State#state{fetchCtx=FetchCtx1}};    
  handle_call({filter_and_sort, _IsSec, FilterSpec, SortSpec, Cols0, _SKey}, _From, #state{statement=Stmt}=State) ->
  