Re: Auto-tuning work_mem and maintenance_work_mem

* Bruce Momjian (bruce(at)momjian(dot)us) wrote:
> On Thu, Oct 10, 2013 at 07:24:26AM -0700, Kevin Grittner wrote:
> > Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> > > I actually had the thought that it might be something we'd integrate
> > > *into* initdb.  So you'd do initdb --system-memory 8GB or something
> > > like that and it would do the rest.  That'd be slick, at least IMHO.
> >
> > How would you handle the case that the machine (whether physical or
> > a VM) later gets more RAM?  That's certainly not unheard of with
> > physical servers, and with VMs I'm not sure that the database
> > server would necessarily go through a stop/start cycle for it.
>
> Yes, going from a non-dedicated to a dedicated database server, adding
> RAM, or moving the cluster to another server could all require an initdb
> to change auto-tuned values. This is why I think we will need to
> auto-tune in the backend, rather than via initdb. I do think an
> available_mem parameter for initdb would help though, to be set in
> postgresql.conf.

For this case, I think the suggestion made by MauMau would be better-
tell the user (in the postgresql.conf comments) a command they can run
with different memory settings to see what the auto-tuning would do.
Perhaps even have a way to enable use of those new variables, but I
don't really care for the idea of making a GUC that isn't anything
except a control for defaults of *other* GUCs.

Thanks,

Stephen