Re: WIP: Avoid creation of the free space map for small tables

On Fri, Nov 2, 2018 at 7:23 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> > That doesn't seem like an unreasonable argument.  I'm not sure whether
> > the right threshold is 4 or something a little bigger, but I bet it's
> > not very large.  It seems important to me that before anybody thinks
> > about committing this, we construct some kind of destruction case
> > where repeated scans of the whole table are triggered as frequently as
> > possible, and then run that test with varying thresholds.
>
> Why do you think repeated scans will be a destruction case when there
> is no FSM for a small table?

That's not what I'm saying.  If we don't have the FSM, we have to
check every page of the table.  If there's a workload where that
happens a lot on a table that is just under the size threshold for
creating the FSM, then it's likely to be a worst case for this patch.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company