On 11/10/2012 02:08 PM, Scott Marlowe wrote:
> On Sat, Nov 10, 2012 at 2:12 PM, Jeff Janes <jeff.janes@gmail.com> wrote:
>> On Fri, Nov 9, 2012 at 5:56 PM, Scott Marlowe <scott.marlowe@gmail.com> wrote:
>>>
>>> As well, since the default nap time is 1 minute, it will take at least
>>> 50 minutes to vacuum each db as nap time is how long autovac waits
>>> between databases.
>>
>> That isn't how it works. The naptime is per database, not per
>> cluster. If the naptime is 1 minute and there are 50 "active"
>> databases, then it will launch a new worker every 1.2 seconds
>> (assuming the old ones finish fast enough that doing so would not
>> exceed autovacuum_max_workers)
>
> Hmmm. That was not my understanding from previous discussions on nap time.
>
>
When in doubt there are the docs:)
http://www.postgresql.org/docs/9.1/interactive/routine-vacuuming.html#AUTOVACUUM
"The "autovacuum daemon" actually consists of multiple processes. There
is a persistent daemon process, called the autovacuum launcher, which is
in charge of starting autovacuum worker processes for all databases. The
launcher will distribute the work across time, attempting to start one
worker within each database every autovacuum_naptime seconds.
(Therefore, if the installation has N databases, a new worker will be
launched every autovacuum_naptime/N seconds.)"
--
Adrian Klaver
adrian.klaver@gmail.com