Re: autovacuum default parameters (was Re: 8.2 is 30% better in pgbench than 8.3)

Alvaro Herrera wrote:
> Gregory Stark wrote:
>> "Alvaro Herrera" <alvherre@commandprompt.com> writes:
>>
>>>> Alvaro Herrera <alvherre@commandprompt.com> writes:
>>>>> I am taking the liberty to also lower the vacuum and analyze threshold
>>>>> default values to 50, per previous discussion.
>> Did we also reach any consensus about lowering the percentage of dead tuples
>> in a table before we trigger vacuum? I think 20% is way too high and 5% is
>> saner. I actually think it would be better even lower but would be ok with 5%.
> 
> We didn't, but while I agree with the idea, I think 5% is too low.  I
> don't want autovacuum to get excessively aggressive.  Is 10% not enough?

It depends really. 10% on a small table seems like a waste except that 
small tables are quick to vacuum. 10% on a table with 20 million rows, 
is a lot of dead rows.

Joshua D. Drake


> 
> How about the analyze scale factor, should we keep the current 10%?  I
> have less of a problem with reducing it further since analyze is cheaper
> than vacuum.
> 


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