void SPI_cursor_fetch(Portal portal, bool forward, long count)
SPI_cursor_fetch fetches some rows from a cursor. This is equivalent to a subset of the SQL command FETCH (see SPI_scroll_cursor_fetch for more functionality).
portal containing the cursor
true for fetch forward, false for fetch backward
maximum number of rows to fetch
SPI_processed and SPI_tuptable are set as in SPI_execute if successful.
Fetching backward may fail if the cursor's plan was not created with the CURSOR_OPT_SCROLL option.