Re: MVCC performance issue

On Sat, Nov 13, 2010 at 07:53, Craig Ringer <craig@postnewspapers.com.au> wrote:
> Oracle's MVCC approach has its own costs. Like Pg's, those costs increase
> with update/delete frequency. Instead of table bloat, Oracle suffers from
> redo log growth (or redo log size management issues). Instead of increased
> table scan costs from dead rows, Oracle suffers from random I/O costs as it
> looks up the out-of-line redo log for old rows. Instead of long-running
> writer transactions causing table bloat, Oracle can have problems with
> long-running reader transactions aborting when the redo log runs out of
> space.

Another advantage of Oracle's approach seems that they need much less
tuple-level overhead. IMO the 23-byte tuple overhead is a much bigger
drawback in Postgres than table fragmentation.

Regards,
Marti