Re: Vacuum verbose output?

On 14/1/03 16:10, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Julian Scarfe <julian(dot)scarfe(at)ntlworld(dot)com> writes:
>> On 14/1/03 15:42, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> What do you have the FSM parameters in postgresql.conf set to? My guess
>>> is you need to increase 'em.
>
>> Currently set at the defaults, max_fsm_relations is 100, max_fsm_pages is
>> 10000.
>
> 100 is definitely too small for max_fsm_relations; we've bumped that
> default to 1000 for the next release. Given that you've got a
> nearly-100k-page table, 10000 for max_fsm_pages is probably much too
> small also.
>
>> What are the implications/effects of increasing them?
>
> Shared memory usage gets bigger. I think the max_fsm_pages multiplier
> is 6 bytes per slot, so you could make it a million, or ten, without
> stressing modern machines. I'd try 1000/1000000 for starters.

OK, so what's the up-side? :-)

Will this improve performance, or change disk space requirements, or
something else? What's the rule of thumb, what are the criteria for setting
these parameters?

Unfortunately, I don't have enough of a grasp of the internals to understand
the implications of the changes -- is there a particular section of the doc
that would help me, or do I have to look at the source? At the moment, I
don't have a good mental model of what's going on.

Thanks again

Julian