Re: Max compact as an FSM strategy

On Tue, 26 Jul 2022 at 11:02, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>
> On Tue, Jul 26, 2022 at 3:04 PM Simon Riggs
> <simon(dot)riggs(at)enterprisedb(dot)com> wrote:
> >
> > A long time ago, Tom Lane came up with the idea that when tables get
> > bloated, tables might be allowed to shrink down again in size
> > naturally by altering the way FSM allocates blocks. That's a very good
> > idea, but we didn't implement it back then...
> >
> > This patch allows the Heap to specify what FreeSpaceStrategy it would
> > like to see.

> I think this is a really interesting idea. So IIUC this patch enables
> an option to select between the strategy but don't yet decide on that.

Correct

> > All we need is a simple heuristic to allow us to choose between
> > various strategies.
>
> I think it would be really interesting to see what would be the exact
> deciding point between these strategies. Because when we switch from
> CONCURRENCY to COMPACT it would immediately affect the insert/update
> performance but it would control the bloat. So I am not sure whether
> the selection should be completely based on the heuristic or there
> should be some GUC parameter where the user can decide at what point
> we should switch to the COMPACT strategy or it should not at all
> switch?

How and when is the right question. I am happy to hear thoughts and
opinions from others before coming up with a specific scheme to do
that.

--
Simon Riggs http://www.EnterpriseDB.com/