Re: optimization ideas for frequent, large(ish) updates in frequently accessed DB?

Marinos,

> shared_buffers=100000
> (I tried many values, this seems to work well for us - 12GB RAM)
> wal_buffers=500
> sort_mem=800000
> checkpoint_segments=16
> effective_cache_size=1000000
> etc.

800MB for sort mem?   Are you sure you typed that correctly?   You must be
counting on not having a lot of concurrent queries.  It sure will speed up
index updating, though!

I think you might do well to experiment with using the checkpoint_delay and
checkpoint_sibilings settings in order to get more efficient batch processing
of updates while selects are going on.  I would also suggest increasing
checkpoint segments as much as your disk space will allow; I know one
reporting database I run that does batch loads is using 128 (which is about a
gig of disk, I think).

What have you set max_fsm_relations and max_fsm_pages to?  The latter should
be very high for you, like 10,000,000

For that matter, what *version* of PostgreSQL are you running?

Also, make sure that your tables get vaccuumed regularly.

> Any help/suggestions would be greatly appreciated... Even if it's
> something like "you need a faster db box, there's no other way" ;-)

Well, a battery-backed RAID controller with a fast cache would certainly help.

You'll also be glad to know that a *lot* of the improvements in the upcoming
PostgreSQL 7.5 are aimed at giving better peformance on large, high-activity
databases like yours.

--
-Josh Berkus
 Aglio Database Solutions
 San Francisco