Producing Data Using fetch_into

Use the fetch_into API method to produce data.

1. Set num_rows to a value based on the number of rows produced in the fetch call.
2. For each row produced, set the row_status flag of a_v4_extfn_row to 1 (available) or 0 (not available). The default value is 1.
3. For each column (a_v4_extfn_column_data) in the row set:

   Options	Description
   is_null	Set to true, if the value returned is NULL. The default is false.
   data	The data returned must be copied into this pointer
   piece_len	The actual length of data returned. For fixed-length data types, this cannot exceed max_piece_len. Defaults to max_piece_len for fixed data types.

4. For each column, return 1 to indicate rows produced, and return 0 to indicate otherwise.