"Iain" <iain@mst.co.jp> writes:
>> another way to speed up full vacuum?
> Hmmm... a full vacuum may help to re-organize the structure of modified
> tables, but whether this is significant or not is another matter.
Actually, VACUUM FULL is designed to work nicely for the situation where
a table has say 10% wasted space and you want the wasted space all
compressed out. When there is a lot of wasted space, so that nearly all
the rows have to be moved to complete the compaction operation, VACUUM
FULL is not a very good choice. And it simply moves rows around, it
doesn't modify the rows internally; so it does nothing at all to reclaim
space that would have been freed up by DROP COLUMN operations.
CLUSTER is actually a better bet if you want to repack a table that's
suffered a lot of updates or deletions. In PG 8.0 you might also
consider one of the rewriting variants of ALTER TABLE.
regards, tom lane
