Re: Vacuum verbose output?

[Sorry about the false start.]

On 14/1/03 16:32, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Julian Scarfe <julian(dot)scarfe(at)ntlworld(dot)com> writes:
>> OK, so what's the up-side? :-)
>
>> Will this improve performance, or change disk space requirements, or
>> something else?
>
> It'll keep the system from leaking free space in tables, which is what's
> causing your tables to bloat. You need an FSM slot for each page that
> has useful free space on it, else the system will forget about that
> free space.

OK, makes sense.

>> What's the rule of thumb, what are the criteria for setting
>> these parameters?
>
> Right at the moment I don't think there is any direct way to discover
> how big max_fsm_pages needs to be. An upper bound is
> select sum(relpages) from pg_class where relkind in ('r','t');
> (actually you have to sum over all databases in your installation).
> But in most scenarios this is probably overkill, as large tables tend
> not to have turnover in every page.

In my case, for this, the only seriously active database

=> select sum(relpages) from pg_class where relkind in ('r','t');
sum
--------
858596
(1 row)

So it looks like your guess of 1000000 is pretty much spot on.

We'll see how that goes.

Thanks for the help

Julian