Cursors: getting the number of tuples; moving backwards

Hello everyone!

I have 2 questions:

--1-- Some days ago, I've been trying to get the number of tuples
that FETCH ALL would return, *before* fetching anything.
(the program is written in C++, using libpq ; PostgreSQL 7.2.3).

The solution i've found was something like:

int nr_tuples;

res = PQexec(conn, "MOVE ALL in CURS");
sscanf(PQcmdStatus(res),"MOVE %i",&nr_tuples);
PQclear(res);

I'm wondering: is there any better way to get that number?

( just an idea: maybe it would be useful to make PQcmdTuples
work for MOVE commands ... ? )

--2-- I found out that if i reach the end of the cursor, and want
to move backwards, i have to increase the MOVE command's argument by 1:

MOVE ALL in CURS --> i get the number of tuples: 590

MOVE -590 in CURS
FETCH ALL --> i get all tuples except the first one

MOVE -591 in CURS
FETCH ALL --> i get all the tuples

MOVE -1 in CURS
FETCH ALL --> i get nothing !

MOVE -2 in CURS
FETCH ALL --> i get the last tuple

This happens only if the current position is at the end of the cursor.

Is this the normal behaviour?

Best regards,
Adrian Maier
(am(at)fx(dot)ro)