Re: reclaiming disk space after major updates

On Wed, Jun 06, 2007 at 04:04:44PM -0600, Dan Harris wrote:
> of these operations or a full dump/reload. I do run VACUUM regularly, it's
> just that sometimes we need to go back and update a huge percentage of rows
> in a single batch due to changing customer requirements, leaving us with
> significant table bloat.

Do you need to update those rows in one transaction (i.e. is the
requirement that they all get updated such that the change only
becomes visible at once)? If not, you can do this in batches and
vacuum in between. Batch updates are the prime sucky area in
Postgres.

Another trick, if the table is otherwise mostly static, is to do the
updating in a copy of the table, and then use the transactional DDL
features of postgres to change the table names.

A

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