/*
 * call-seq:
 *    res.oid_value() -> Fixnum
 *
 * Returns the +oid+ of the inserted row if applicable,
 * otherwise +nil+.
 */
static VALUE
pgresult_oid_value(VALUE self)
{
    Oid n = PQoidValue(get_pgresult(self));
    if (n == InvalidOid)
        return Qnil;
    else
        return INT2FIX(n);
}