On Mon, Jan 22, 2007 at 06:42:09PM +0000, Simon Riggs wrote:
> On Mon, 2007-01-22 at 13:27 -0500, Bruce Momjian wrote:
> > Yep, agreed on the random I/O issue. The larger question is if you have
> > a huge table, do you care to reclaim 3% of the table size, rather than
> > just vacuum it when it gets to 10% dirty? I realize the vacuum is going
> > to take a lot of time, but vacuuming to relaim 3% three times seems like
> > it is going to be more expensive than just vacuuming the 10% once. And
> > vacuuming to reclaim 1% ten times seems even more expensive. The
> > partial vacuum idea is starting to look like a loser to me again.
>
> Hold that thought! Read Heikki's Piggyback VACUUM idea on new thread...
>
> --
> Simon Riggs
> EnterpriseDB http://www.enterprisedb.com
>
There may be other functions that could leverage a similar sort of
infrastructure. For example, a long DB mining query could be registered
with the system. Then as the pieces of the table/database are brought in
to shared memory during the normal daily DB activity they can be acquired
without forcing the DB to run a very I/O expensive query when waiting a
bit for the results would be acceptable. As long as we are thinking
piggyback.
Ken