Re: Why vacuum?

* Daniele Orlandi <daniele(at)orlandi(dot)com> [001214 09:10] wrote:
> Zeugswetter Andreas SB wrote:
> >
> > If the priority is too low you will end up with the same behavior as current,
>
> Yes, and it is the intended behaviour. I'd use idle priority for it.

If you're talking about vacuum, you really don't want to do this,
what's going to happen is that since you have an exclusive lock on
the file during your vacuum and no way to do priority lending you
can deadlock.

> > because the cache will be emptied by high priority multiple new rows,
> > thus writing to the end anyways.
>
> Yes, but this only happens when you don't have enought spare idle CPU
> time. If you are in such situation for long periods, there's nothing you
> can do, you already have problems.
>
> My approach in winning here because it allows you to have bursts of CPU
> utilization without being affected by the overhead of a overwriting smgr
> that (without hacks) will always try to find available slots, even in
> high load situations.
>
> > Conclusio: In those cases where overwrite would be most advantageous (high
> > volume modified table) your system won't work
>
> Why ? I have plenty of CPU time available on my server, even if one of
> my table is highly volatile, fast-changing.

When your table grows to be very large you'll see what we're talking
about.

--
-Alfred Perlstein - [bright(at)wintelcom(dot)net|alfred(at)freebsd(dot)org]
"I have the heart of a child; I keep it in a jar on my desk."