On Thu, Jun 26, 2008 at 02:40:59PM +0200, Holger Hoffstaette wrote: > large databases treat mass updates? AFAIK both DB2 and Oracle use MVCC > (maybe a different kind?) as well, but I cannot believe that large updates > still pose such big problems.
DB2 does not use MVCC. This is why lock escalation is such a big problem for them. Oracle uses a kind of MVCC based on rollback segments: your work goes into the rollback segment, so that it can be undone, and the update happens in place. This causes a different kind of pain: you can run out of rollback segments (part way through a long-running transaction, even) and then have to undo everything in order to do any work at all. Every system involves trade-offs, and different systems make different ones. The bulk update problem is PostgreSQL's weak spot, and for that cost one gets huge other benefits. > Are there no options (algorithms) for adaptively choosing different > update strategies that do not incur the full MVCC overhead? How would you pick? But one thing you could do is create the table with a non-standard fill factor, which might allow HOT to work its magic. A -- Andrew Sullivan [EMAIL PROTECTED] +1 503 667 4564 x104 http://www.commandprompt.com/ -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
