Re: [S] Re: Problems with non scrollable cursors

Kris Jurka wrote:

>On Mon, 24 Jan 2005, Daniele Bufarini wrote:
>
>
>
>>Actually using the cursor multiple time is what I was thinking...
>>In fact, I can keep an open database connection only for large result
>>set and use a one time connection for all the others.
>>My problem is that I cannot scroll back using a cursor... I'm wondering
>>If I have to modify the jdbc driver or the back end or if there are
>>other solutions, less time consuming...
>>
>>
>
>The easiest thing to do is to forgo parts of the JDBC interface and do it
>manually.
>
>Statement.execute("DECLARE mycursor SCROLL CURSOR FOR ...");
>
>Then:
>
>Statement.execute("MOVE ABSOLUTE 2000 IN mycursor");
>ResultSet = Statement.executeQuery("FETCH FORWARD 10 FROM mycursor");
>
>
>To fix this in the driver there are two avenues of attack here.  The 7.4
>driver used explicit DECLARE and FETCH calls for cursors.  The driver
>would need to be modified to add a SCROLL keyword and then handle moving
>back and forth.  A patch was produced to do this, which I had some
>concerns about, that the poster never responded to:
>
>http://archives.postgresql.org/pgsql-jdbc/2004-05/msg00164.php
>
>The 8.0 driver has been changed to use protocol level portals which are
>pretty much the same as cursors.  The problem is that protocol only
>has support for forward cursors in both declaration and fetching.  To fix
>things along these lines would require pretty much all of the work in the
>driver as the 7.4 path, but would also require some backend work and more
>importantly, convincing people to change the frontend/backend protocol.
>

Thank you very much for your explanations, Kris!
First I'll try to use cursors without the JDBC interface: If that
shouldn't work as required, I'll consider the two other avenues of attack.
I'll let you know...

                Best regards,
                    Daniele Bufarini.