On Sun, 2007-01-21 at 14:26 -0600, Jim C. Nasby wrote: > 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. err...It doesn't do this now and IIRC didn't do that in 8.1 either. > 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. True, but not recommended, though for a variety of reasons. The reason is not intermediate commits, but just that the work of VACUUM is mostly non-transactional in nature, apart from the various catalog entries when it completes. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com
