Re: visibility map - what do i miss?

On Sat, Dec 6, 2008 at 12:53 PM, hubert depesz lubaczewski
<depesz(at)depesz(dot)com> wrote:
> First run - without visibility maps, timing of vacuums:
> Time: 267844.822 ms
> Time: 138854.592 ms
> Time: 305467.950 ms
> Time: 487133.179 ms
>
> Second run - on head:
>
> Time: 252218.609 ms
> Time: 234388.763 ms
> Time: 334016.413 ms
> Time: 575698.750 ms
>
> Now - as I understand the change - visilibity maps should make second run much faster?

If I understand correctly what Heikki explained, not if you run VACUUM
only once (and you confirmed me on IRC you run it only once). It's the
VACUUM which sets the PD_ALL_VISIBLE flag on the pages so the first
VACUUM should be slower with HEAD than with 8.3 as it has far more
work to do.

The second VACUUM should then be faster.

--
Guillaume