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

On Mon, 2020-03-16 at 12:53 +0900, Masahiko Sawada wrote:
> There is already a consensus on introducing new 2 parameters, but as
> the second idea I'd like to add one (or two) GUC(s) to my suggestion,
> say autovacuum_vacuum_freeze_insert_ratio; this parameter is the ratio
> of the number of inserted tuples for total number of tuples modified
> and inserted, in order to trigger insert-only vacuum. For example,
> suppose the table has 1,000,000 tuples and we set threshold = 0,
> scale_factor = 0.2 and freeze_insert_ratio = 0.9, we will trigger
> normal autovacuum when n_dead_tup + n_ins_since_vacuum > 200,000, but
> we will instead trigger insert-only autovacuum, which is a vacuum with
> vacuum_freeze_min_age = 0, when n_ins_since_vacuum > 180,000 (=200,000
> * 0.9). IOW if 90% of modified tuples are insertions, we freeze tuples
> aggressively. If we want to trigger insert-only vacuum only on
> insert-only table we can set freeze_insert_ratio = 1.0. The down side
> of this idea is that we cannot disable autovacuum triggered by the
> number of inserted, although we might be able to introduce more one
> GUC that controls whether to include the number of inserted tuples for
> triggering autovacuum (say, autovacuum_vacuum_triggered_by_insert =
> on|off). The pros of this idea would be that we can ensure that
> insert-only vacuum will run only in the case where the ratio of
> insertion is large enough.

Two more parameters :^(  But your reasoning is good.

How about we go with what we have now and leave that for future
discussion and patches?

Yours,
Laurenz Albe