I don't know if this would work, but if you just want to restructure your
rows, your could do this:
UPDATE table SET id = id WHERE id BETWEEN 0 AND 20000;
VACUUM table;
UPDATE table SET id = id WHERE id BETWEEN 20001 AND 40000;
VACUUM table;
wash, rinse, repeat.
The idea is that an update rewrites the rows (in your new format) and
that VACUUM (not FULL) is quite fast when you just modified a part of the
table, and non-locking.
Would this work ?
> "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
>
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