Hi Tomas,
Unfortunately I think you are mistaken - disabling the stats collector
(i.e. track_counts = off) means that autovacuum has no idea about
when/if it needs to start a worker (as it uses those counts to decide),
and hence you lose all automatic vacuum and analyze as a result.
With respect to comments like "it shouldn't make difference" etc etc,
well the profile suggests otherwise, and the change in tps numbers
support the observation.
regards
Mark
On 30/07/14 20:42, Tomas Vondra wrote:
> On 30 Červenec 2014, 3:44, Mark Kirkwood wrote:
>>
>> While these numbers look great in the middle range (12-96 clients), then
>> benefit looks to be tailing off as client numbers increase. Also running
>> with no stats (and hence no auto vacuum or analyze) is way too scary!
>
> I assume you've disabled statistics collector, which has nothing to do
> with vacuum or analyze.
>
> There are two kinds of statistics in PostgreSQL - data distribution
> statistics (which is collected by ANALYZE and stored in actual tables
> within the database) and runtime statistics (which is collected by the
> stats collector and stored in a file somewhere on the dist).
>
> By disabling statistics collector you loose runtime counters - number of
> sequential/index scans on a table, tuples read from a relation aetc. But
> it does not influence VACUUM or planning at all.
>
> Also, it's mostly async (send over UDP and you're done) and shouldn't make
> much difference unless you have large number of objects. There are ways to
> improve this (e.g. by placing the stat files into a tmpfs).
>
> Tomas
>