To use a cursor behind the scenes would require the jdbc driver to have its own begin/end block. Because the connection is shared, there is nothing that prevents someone else from trying to execute a begin/end/commit/rollback statement that would screw up the driver. So it would need a seperate connection for each scrollable resultset.
Kovács Péter wrote: > I am afraid I do not understand your explanation. What do you mean by > "begin/end block"? I am thinking in terms of simple SQL statements like: > > begin; > declare myc cursor for select * from mm_history; > fetch forward 2 in myc; > close myc; > rollback; (or if you did some update in the same transaction: commit;) > > > >>-----Original Message----- >>From: Joseph Shraibman [mailto:[EMAIL PROTECTED]] >>Sent: Tuesday, October 16, 2001 11:54 PM >>To: Kovács Péter >>Cc: [EMAIL PROTECTED] >>Subject: Re: JDBC 2 ResultSet and cursors >> >> >>Because the driver would have to dedicate a connection to the >>backend to the resultset to >>make sure nobody else tries to begin/end a block while it is >>trying to use a cursor. >>(that's the simple explanation) Since a connection to the >>backend currently requires a >>fork, it would be a real resource hog. >> >>Kovács Péter wrote: >> >> >>>Hi, >>> >>>I have a question for which I can think of an answer, but still I am >>>uncertain about it. >>> >>>Why the scrollable result sets are not implemented in the >>> >>current jdbc >> >>>driver? Is it technically impossible or just no one needed >>> >>this feature yet? >> >>>The answer is probably that due to the lack of backend >>> >>support for updatable >> >>>cursors the scrollable result set would not be fully >>> >>functional. (On the >> >>>face of it, I think that it should be possible to build support for >>>read-only scrollable result set into the jdbc driver.) But >>> >>would a halfway >> >>>solution not be better than nothing? You need to resort to >>> >>workarounds >> >>>anyway, if you want to use cursor based data processing >>> >>with PostgreSQL. >> >>>IMHO, a read-only scrollable result set would definitly be >>> >>an important step >> >>>toward code portability. >>> >>>Any comments? >>> >>>Does anyone have info on whether there are plans to >>> >>implement support for >> >>>updatable cursors in the backend? If there are, what are they? >>> >>>Thank you >>> >>>Peter >>> >>>---------------------------(end of >>> >>broadcast)--------------------------- >> >>>TIP 2: you can get off all lists at once with the unregister command >>> (send "unregister YourEmailAddressHere" to >>> >>[EMAIL PROTECTED]) >> >> >>-- >>Joseph Shraibman >>[EMAIL PROTECTED] >>Increase signal to noise ratio. http://www.targabot.com >> >> -- Joseph Shraibman [EMAIL PROTECTED] Increase signal to noise ratio. http://www.targabot.com ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
