Re: Impact of vacuum full...

On Fri, 2006-07-21 at 15:49, Erik Jones wrote:
> Scott Marlowe wrote:
> >
> > I'd use regular cronned vacuums on the tables that you know grown a lot
> > (or just hit the whole db and not worry about it) and run occasional
> > vacuum verbose / vacuum full verbose by hand to see if you have problems
> > with your Free Space Map being too small.
> >
> Awesome! Thanks, guys, for all of your input/advice. That's pretty
> much how I thought stuff worked after reading the docs but was
> confused/misled by other inputs. With regards to the Free Space Map and
> max_fsm_relations: is using the value of "SELECT COUNT(*) FROM
> pg_class;" plus some room for growth a good way to set that?

I always use vacuum verbose to see that. At the end, it'll have a part
that looks like this:

INFO: free space map: 35 relations, 18903 pages stored; 17504 total
pages needed
DETAIL: Allocated FSM size: 5000 relations + 100000 pages = 894 kB
shared memory.
VACUUM

So, on this machine, we can handle 5000 relations of 100,000 total
pages, and we're only uses the space of 35 relations and ~20,000 pages.

If the pages needed exceeds the allocated size, you've got problems.

You've got to run the database for a while to see what the state will be
like over time.