for PL/Perl, to avoid loading the entire result set into memory as the
existing spi_exec_query() function does.

Here's how one might use the new functions:

    $x = spi_query("select ...");
    while (defined ($y = spi_fetchrow($x))) {
        ...
        return_next(...);
    }

The changes do not affect the spi_exec_query() interface in any way.

Abhijit Menon-Sen