[postgis-users] Large Databases

[Jim C. Nasby]

On Tue, Jun 13, 2006 at 12:02:41PM -0600, Michael Fuhr wrote:
> On Tue, Jun 13, 2006 at 01:05:21PM -0400, Robert Burgholzer wrote:
> > This is off topic, but I was under the impression that vacuum full was
> > actually the only vacuum that re-cycled used disk space?
> 
> VACUUM without FULL marks dead space for reuse but doesn't release
> it back to the filesystem (i.e., it doesn't shrink the file).  VACUUM

Actually, AFAIK a lazy (ie: plain) vacuum will return unused space from
the very end of a table. So if you can't take the hit to run VACUUM FULL
on a bloated table, you can update all the tuples on the last X pages in
the table enough times to fill those pages and move all the tuples
somewhere else in the table, and then vacuum.

Unfortunately, it's much, much harder (if not impossible) to do the same
thing with indexes.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby at pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461