Re: [HACKERS] Autovacuum Improvements

On Sun, Jan 21, 2007 at 11:39:45AM +0000, Heikki Linnakangas wrote:
> Russell Smith wrote:
> >Strange idea that I haven't researched,  Given Vacuum can't be run in a
> >transaction, it is possible at a certain point to quit the current
> >transaction and start another one.  There has been much chat and now a
> >TODO item about allowing multiple vacuums to not starve small tables.
> >But if a big table has a long running vacuum the vacuum of the small
> >table won't be effective anyway will it?  If vacuum of a big table was
> >done in multiple transactions you could reduce the effect of long
> >running vacuum.  I'm not sure how this effects the rest of the system
> >thought.
>
> That was fixed by Hannu Krosing's patch in 8.2 that made vacuum to
> ignore other vacuums in the oldest xmin calculation.

And IIRC in 8.1 every time vacuum finishes a pass over the indexes it
will commit and start a new transaction. That's still useful even with
Hannu's patch in case you start a vacuum with maintenance_work_mem too
small; you can abort the vacuum some time later and at least some of the
work it's done will get committed.
--
Jim Nasby                                            jim@nasby.net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)