[postgis-users] Large Databases

[Markus Schaber]

Hi, Robert,

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?

AFAIK, plain VACUUM can only return completely free pages to the OS from
the end of file, whileas VACUUM FULL actively moves rows between pages
to create such completely free pages.

They both register partially freed pages into the free space map.

CLUSTER actually completely rebuilds the table by reading the original
table in index order, and deleting the original table afterwards, so it
also tends to free space, but needs a considerable amount of temp space.

HTH,
Markus
-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

Fight against software patents in EU! www.ffii.org www.nosoftwarepatents.org