Martijn van Oosterhout wrote:
> On Thu, Apr 26, 2007 at 12:13:13AM +0200, Listmail wrote:
> > VACUUM FULL is slow because it plays with the indexes...
> > CLUSTER is slow because it has to order the rows...
>
> And:
> VACUUM FULL has to seek/read/write all over the disk to get it's job
> done.
> CLUSTER can scan through the table linearly a few times and write out
> the result.
> Now it's true that sorting large files involves overflowing to disk,
> but that path has been pretty well optimised.
Hmm, no, CLUSTER doesn't scan the table linearly; it uses an indexscan,
so it also needs seek/read/seek/read/write.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.
