On Sun, 2007-07-22 at 08:53 -0700, Josh Berkus wrote:
> Pavel Stehule wrote:
> > Hello,
> > 
> > I checked my tests again I have different results. Now I tested
> > PostgreSQL on dedicated server. Now 8.3 is about 20% faster. I didn't
> > see strong  impression of autovacuum.  All numbers are approximate
> > only. I did pgbench 3x for folowing configuration: (autovacuum on,
> > autovacuum off, statistics off) and for -tntransaction (100, 1000,
> > 4000)
> In other news, 8.3 with current HOT is 13% faster than 8.2 at TPCE in 
> the first 1/2 hour.  Performance does not fall over 5 hours of test run, 
> and most of the main tables never have autovacuum triggered at all. 
> Unfortnately, we don't yet have a 5-hour 8.2 run to compare 
> last-half-hour performance.

I think the rule of thumb is if the workload doesn't have enough UPDATEs
to trigger VACUUMs then HOT will have a low benefit.

With any workload, we should run it *until* we see some autovacuums
kick-in, so we can compare the overall situation of HOT v non-HOT. HOT
is designed for longer term benefit; fillfactor benefits fade over time
(as defined).

  Simon Riggs
  EnterpriseDB  http://www.enterprisedb.com

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