Re: Autovacuum launcher doesn't notice death of postmaster immediately

Alvaro Herrera wrote:
> Matthew T. O'Connor escribió:
> 
>> Ok, but I think the question posed is that in say a virtual hosting 
>> environment there might be say 1,000 databases in the cluster.

That is uhmmm insane... 1000 databases?

Joshua D. Drake


  Am I
>> still going to have to wait a long time for my database to get vacuumed? 
>>  I don't think this has changed much no?
> 
> Depends on how much time it takes to vacuum the other 999 databases.
> The default max workers is 3.
> 
>> (If default naptime is 1 minute, then autovacuum won't even look at a 
>> given database but once every 1,000 minutes (16.67 hours) assuming that 
>> there isn't enough work to keep all the workers busy.)
> 
> The naptime is per database.  Which means if you have 1000 databases and
> a naptime of 60 seconds, the launcher is going to wake up every 100
> milliseconds to check things up.  (This results from 60000 / 1000 = 60
> ms, but there is a minimum of 100 ms just to keep things sane).
> 
> If there are 3 workers and each of the 1000 databases in average takes
> 10 seconds to vacuum, there will be around 3000 seconds between autovac
> runs of your database assuming my math is right.
> 
> I hope those 1000 databases you put in your shared hosting are not very
> big.
> 


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