Re: More vacuum stats

Tom Lane wrote:
> So I'd like to see a positive argument why this is important for users
> to know, rather than merely "we should expose every conceivable detail
> by default".  Why wouldn't a user care more about last AV time for a
> specific table, which we already do expose?
>   

What I actually want here is for the time that the last table autovacuum 
started, adding to the finish time currently exposed by 
pg_stat_user_tables.  "How long did the last {auto}vacuum on <x> take to 
run?" is a FAQ on busy systems here.  If I could compute that from a 
pair of columns, it's a major step toward answering even more 
interesting questions like "how does this set of cost delay parameters 
turn into an approximate MB/s worth of processing rate on my tables?".  
This is too important of a difficult tuning exercise to leave to log 
scraping forever.

I'd rather have that and look at for "SELECT max(last_autovacuum_start) 
FROM pg_stat_user_tables" to diagnose the sort of problems this patch 
seems to aim at helping.

-- 
Greg Smith  2ndQuadrant US  Baltimore, MD
PostgreSQL Training, Services and Support
greg@2ndQuadrant.com   www.2ndQuadrant.us