Jim,

> I'm not going to presume to offer advice on how Firebird should
> handle the problem. Netfrastructure, however, handles the
> ResultSet.isLast() method in approximately to following manner:
>
> throw new SQLException ("Not Yet Implemented")
> ...
> My reasoning is that positional updates have been part of SQL from
> day 0 and are semantically significant while ResultSet.isLast() is
> recent, semantically unnecessary, and absurdly expensive to
> implement.

Interesting enough, Sun provides this information in Javadocs for
ResultSet.isLast(): "Note: Calling the method isLast may be expensive
because the JDBC driver might need to fetch ahead one row in order to
determine whether the current row is the last row in the result set."
So, they are perfectly aware that some servers would require
additional fetch. However I did not find anything about the cursor
position in this case. Also, funny enough, but they do not include
isLast() in JDBC CTS suite (I just checked it). I would say, this
fully confirms your words "is recent, semantically unnecessary, and
absurdly expensive to implement" and makes your implementation
perfectly compatible with JDBC specification! :)

Most likely JayBird will provide different fetchers for
ResultSet.CONCUR_READ_ONLY and ResultSet.CONCUR_UPDATABLE. In
updatable case isLast() will be implemented like in Netfrastructure.

Best regards,
Roman Rokytskyy