Re: Vacuuming Questions

Joshua D. Drake wrote:
> On Wed, 23 Apr 2008 16:27:33 +0100
> John Gardner <john(dot)gardner(at)tagish(dot)co(dot)uk> wrote:
>
>> We have two PostgreSQL servers (8.2) running in a cluster.
>
> Could you be a bit more specific about what you mean by: in a cluster?

Well, we're using middleware technology to load balance and cluster the
PostgreSQL backends

>
>> Now, we're not seeing any problems with performance and we're not
>> seeing any bloat but I have a couple of questions which I hope some
>> of you can help me out on.
>>
>> 1) Is using the autovacuum daemon and running vacuumdb from a cron
>> job overkill?
>
> Not necessarily. Autovacuum can get behind when managing larger tables
> that are actively used. This is better in 8.3 because you can have more
> than one autovacuum worker.
>
>> 2) The vendor of the clustering software suggests that I regularly
>> run vacuum --all --analyze on a specific table. Surely, if I'm
>> running vacuumdb --all --analyze isn't this just a wrapper for
>> running the vacuum --all --analyze command anyway?
>
> Well you have stated two different things here.
>
> 1. The vendor is stating you should vacuum a specific table
> 2. You are vacuuming the whole database.
>
> Do you have a specific table that they are talking about? Is it
> particularly busy? Say a session table?

OK, well initially, the vendor told us to stagger the vacuumdb command
every couple of hours, but latterly they are telling us to vacuum a
specific table. The table contains the transactions that are used for
rollback if any particular node in the cluster needs to be restarted.

>
>> I guess that I'm
>> asking why would I want to run vacuum --all --analyze on a specific
>> table, when I regularly run vacuumdb --all --analyze on all databases?
>>

Thanks

John