Hi Greg,
I've got 32M shared on a 1G machine and 16 checkpoint segments.
I'll run some tests against 64 segments and see what happens.
Your previous postings were extremely helpful wrt the MVCC issue.
I thank you!
-john
Greg Smith wrote:
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
