Re: vacuum full, why multiple times ?

On Wed, Mar 09, 2005 at 02:02:13AM +0100, Gaetano Mendola wrote:

> Basically I'm noticing that a simple vacuum full is not enough to
> shrink completelly the table:
>
> # vacuum full verbose url;
> INFO: vacuuming "public.url"
> INFO: "url": found 268392 removable, 21286 nonremovable row versions in 8563 pages
> DETAIL: 22 dead row versions cannot be removed yet.

How busy is the database? I'd guess that each time you run VACUUM,
there are still open transactions that have visibility to the dead
rows, so VACUUM doesn't touch them. Those transactions eventually
complete, and eventually VACUUM FULL does what you're expecting.
I don't know if that's the only possible cause, but I get results
similar to yours if I have transactions open when I run VACUUM.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/