Re: Berserk Autovacuum (let's save next Mandrill)

On Fri, 13 Mar 2020 at 01:43, Masahiko Sawada
<masahiko.sawada@2ndquadrant.com> wrote:
>
> On Thu, 12 Mar 2020 at 16:28, David Rowley <dgrowleyml@gmail.com> wrote:
> > Laurenz highlighted a seemingly very valid reason that the current
> > GUCs cannot be reused. Namely, say the table has 1 billion rows, if we
> > use the current scale factor of 0.2, then we'll run an insert-only
> > vacuum every 200 million rows. If those INSERTs are one per
> > transaction then the new feature does nothing as the wraparound vacuum
> > will run instead. Since this feature was born due to large insert-only
> > tables, this concern seems very valid to me.
>
> Yeah, I understand and agree that since most people would use default
> values we can reduce mis-configuration cases by adding separate GUCs
> that have appropriate default values for that purpose but on the other
> hand I'm not sure it's worth that we cover the large insert-only table
> case by adding separate GUCs in spite of being able to cover it even
> by existing two GUCs.

In light of the case above, do you have an alternative suggestion?

> If we want to disable this feature on the
> particular table, we can have a storage parameter that means not to
> consider the number of inserted tuples rather than having multiple
> GUCs that allows us to fine tuning. And IIUC even in the above case, I
> think that if we trigger insert-only vacuum by comparing the number of
> inserted tuples to the threshold computed by existing threshold and
> scale factor, we can cover it.

So you're suggesting we drive the insert-vacuums from existing
scale_factor and threshold?  What about the 1 billion row table
example above?