Re: Potential autovacuum optimization: new tables

> [ shrug... ] You're attacking a straw man, or more precisely putting
> words into my mouth about what the percentage-based thresholds might be.
> Notice the examples I gave involved update percentages quite far north
> of 100%. It's possible and maybe likely that we need a sliding scale.

Yes, or a logarithmic one.

> Also, I don't necessarily accept the conclusion you seem to be drawing,
> that it's okay to have complete turnover of a small table and not redo
> its stats.

I'm not drawing that conclusion. I'm explaining the logic of
autovacuum_analyze_threshold. That logic actually works pretty well
for tables between 200 rows and 200,000 rows. It's outside of those
boundaries where it starts to break down.

> The increased number of knobs may be a problem, but I don't think we can
> avoid having more. Your own complaint is that the current design is too
> simplistic. Replacing it with a different but equally simplistic design
> probably won't help much.

Well, we could do something which involves no GUCS at all, which would
be my favorite approach. For example, Frost and I were discussing this
on IRC. Imagine if autovac threshold were set according to a simple log
function, resulting in very small tables getting analyzed after 100%
changes, and very large tables getting analyzed after 0.1% changes, and
everyone else between?

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com