On Fri, 26 Sep 2008, John Huttley wrote:
running update file set perms='0664' took about 10 mins
What do you have checkpoint_segments and shared_buffers set to? If you want something that's doing lots of updates to perform well, you need to let PostgreSQL have a decent size chunk of memory to buffer the index writes with, so it's more likely they'll get combined into larger and therefore more easily sorted blocks rather than as more random ones. The randomness of the writes is why your write rate is so slow. You also need to cut down on the frequency of checkpoints which are very costly on this type of statement.
Also: which version of PostgreSQL? 8.3 includes an improvement aimed at updates like this you might benefit from.
-- * Greg Smith gsmith@xxxxxxxxxxxxx http://www.gregsmith.com Baltimore, MD
