Re: Vacuum wait time problem

>>> Scott Marlowe <scott.marlowe@gmail.com> wrote:
> On Fri, Feb 13, 2009 at 7:02 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Scott Marlowe <scott.marlowe@gmail.com> writes:
>>> On Fri, Feb 13, 2009 at 5:02 PM, Michael Monnerie
>>> <michael.monnerie@is.it-management.at> wrote:
>>>> vacuum_cost_delay = 0
>>>> That was the trick for me. It was set to 250(ms), where it took 5
>>>> hours for a vacuum to run. Now it takes 5-15 minutes.
>>
>>> Wow!!!  250 ms is HUGE in the scheme of vacuum cost delay.  even
>>> 10ms is usually plenty to slow down vacuum enough to keep it out
>>> of your way and double to quadruple your vacuum times.
>>
>> I wonder whether we ought to tighten the allowed range of
>> vacuum_cost_delay.  The upper limit is 1000ms at the moment;
>> but that's clearly much higher than is useful, and it seems
>> to encourage people to pick silly values ...
>
> I agree.  I can't imagine using a number over 50 or so.

I don't know what other people have found useful, but when I
experimented with this in our environment, it seemed like I should
just treat vacuum_cost_delay as a boolean, where 0 meant off and 10
meant on, and tune it by adjusting vacuum_cost_limit.  The granularity
of vacuum_cost_delay is course and surprising unpredictable.

-Kevin