Re: New GUC autovacuum_max_threshold ?

Le 26/04/2024 à 04:24, Laurenz Albe a écrit :
> On Thu, 2024-04-25 at 14:33 -0400, Robert Haas wrote:
>> I believe that the underlying problem here can be summarized in this
>> way: just because I'm OK with 2MB of bloat in my 10MB table doesn't
>> mean that I'm OK with 2TB of bloat in my 10TB table. One reason for
>> this is simply that I can afford to waste 2MB much more easily than I
>> can afford to waste 2TB -- and that applies both on disk and in
>> memory.
> 
> I don't find that convincing.  Why are 2TB of wasted space in a 10TB
> table worse than 2TB of wasted space in 100 tables of 100GB each?
> 

Good point, but another way of summarizing the problem would be that the 
autovacuum_*_scale_factor parameters work well as long as we have a more 
or less evenly distributed access pattern in the table.

Suppose my very large table gets updated only for its 1% most recent 
rows. We probably want to decrease autovacuum_analyze_scale_factor and 
autovacuum_vacuum_scale_factor for this one.

Partitioning would be a good solution, but IMHO postgres should be able 
to handle this case anyway, ideally without per-table configuration.