SPI_scroll_cursor_fetch — fetch some rows from a cursor
void SPI_scroll_cursor_fetch(Portalportal, FetchDirectiondirection, longcount)
   SPI_scroll_cursor_fetch fetches some rows from a
   cursor.  This is equivalent to the SQL command FETCH.
  
Portal portalportal containing the cursor
FetchDirection direction
      one of FETCH_FORWARD,
      FETCH_BACKWARD,
      FETCH_ABSOLUTE or
      FETCH_RELATIVE
     
long count
      number of rows to fetch for
      FETCH_FORWARD or
      FETCH_BACKWARD; absolute row number to fetch for
      FETCH_ABSOLUTE; or relative row number to fetch for
      FETCH_RELATIVE
     
   SPI_processed and
   SPI_tuptable are set as in
   SPI_execute if successful.
  
   See the SQL FETCH command
   for details of the interpretation of the
   direction and
   count parameters.
  
   Direction values other than FETCH_FORWARD
   may fail if the cursor's plan was not created
   with the CURSOR_OPT_SCROLL option.