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