On Wed, 24 Mar 2004, pginfo wrote:
> Hi,
>
> I am running pg 7.4.1 on linux box.
> I have a midle size DB with many updates and after it I try to run
> vacuum full analyze.
Is there a reason to not use just regular vacuum / analyze (i.e. NOT
full)?
> It takes about 2 h.
Full vacuums, by their nature, tend to be a bit slow. It's better to let
the database achieve a kind of "steady state" with regards to number of
dead tuples, and use regular vacuums to reclaim said space rather than a
full vacuum.
> How can I improve the vacuum full analyze time?
>
> My configuration:
>
> shared_buffers = 15000 # min 16, at least max_connections*2,
> 8KB each
> sort_mem = 10000 # min 64, size in KB
You might want to look at dropping sort_mem. It would appear you've been
going through the postgresql.conf file and bumping up numbers to see what
works and what doesn't. While most of the settings aren't too dangerous
to crank up a little high, sort_mem is quite dangerous to crank up high,
should you have a lot of people connected who are all sorting. Note that
sort_mem is a limit PER SORT, not per backend, or per database, or per
user, or even per table, but per sort. IF a query needs to run three or
four sorts, it can use 3 or 4x sort_mem. If a hundred users do this at
once, they can then use 300 or 400x sort_mem. You can see where I'm
heading.
Note that for individual sorts in batch files, like import processes, you
can bump up sort_mem with the set command, so you don't have to have a
large setting in postgresql.conf to use a lot of sort mem when you need
to, you can just grab it during that one session.
> vacuum_mem = 32000 # min 1024, size in KB
If you've got lots of memory, crank up vacuum_mem to the 200 to 500 meg
range and see what happens.
For a good tuning guide, go here:
http://www.varlena.com/varlena/GeneralBits/Tidbits/perf.html
