Re: new autovacuum criterion for visible pages

On 12 August 2016 at 01:01, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
>> In short, autovacuum will need to scan by itself the VM of each
>> relation and decide based on that.
>
> That seems like a worthwhile approach to pursue. The VM is supposed to be
> small, and if you're worried it isn't, you could sample a few pages of it.
> I do not think any of the ideas proposed so far for tracking the
> visibility percentage on-the-fly are very tenable.

Sounds good, but we can't scan the VM for every table, every minute.
We need to record something that will tell us how many VM bits have
been cleared, which will then allow autovac to do a simple SELECT to
decide what needs vacuuming.

Vik's proposal to keep track of the rows inserted seems like the best
approach to this issue.

--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services