Execute the iterator function

After you register an iterator function (and assign it the appropriate privileges), users who have the Execute privilege can execute it. However, because an iterator function returns an active set of items, you must associate the function with a cursor. The cursor holds the active set, which the application can then access one at a time.

Each iteration of the iterator function returns one item of the active set. To execute an iterator function, you must associate it with a cursor. This EXECUTE FUNCTION statement generates an active set that contains the following Fibonacci values:

0, 1, 1, 2, 3, 5, 8

To obtain these values from within an application, you must associate the EXECUTE FUNCTION statement with a cursor to execute the function.

After you register the fibGen() function, you can execute the following SQL statement from an interactive database utility (such as DB-Access):

EXECUTE FUNCTION  fibgen(10);

From within a DataBlade® API module, execute fibGen() with the mi_exec_prepared_statement() function, as follows:

MI_CONNECTION *conn;
mi_string *cmd = "EXECUTE FUNCTION fibgen(10);";
MI_STATEMENT *stmt;
mi_integer error, col_val;
MI_ROW *row;
...
/* Prepare the EXECUTE FUNCTION to execute fibGen() */
stmt = mi_prepare(conn, cmd, NULL);

/* Open the cursor to allocate the active set */
if ( mi_open_prepared_statement(stmt, MI_SEND_READ, 1, 0,
      NULL, NULL, NULL, NULL, NULL, 0, NULL) == MI_OK )

   /* Initialize the fetch direction */
   if ( mi_fetch_statement(stmt, MI_CURSOR_NEXT, 0, 0)
         == MI_OK )

      if ( mi_get_result(conn) == MI_ROWS )
         {
         /* Fetch the items of the active set. 
          * Process each item of active set until 
          * last item is found
          */
         while ( (row = mi_next_row(conn, &error)) != NULL )
            {
            colval = NULL;

            /* Obtain one number of Fibonacci series */
            mi_value(row, 0, (mi_integer)&col_val,
                  sizeof(mi_integer));

                  /* Process current Fibonacci number */
                  ...

            } /* end while */
         } /* end if mi_get_result */

/* Close the cursor to deallocate active set */
mi_close_statement(stmt);

/* Release statement descriptor */
mi_drop_prepared_statement(stmt);

For more information about how to use mi_exec_prepared_statement(), see Execute prepared SQL statements.