On Tue, 2007-04-10 at 11:40 +0100, Heikki Linnakangas wrote: > Tom Lane wrote: > > Heikki Linnakangas <[EMAIL PROTECTED]> writes: > >> I've been working on the patch to enhance our group commit behavior. The > >> patch is a dirty hack at the moment, but I'm settled on the algorithm > >> I'm going to use and I know the issues involved. > > > > One question that just came to mind is whether Simon's no-commit-wait > > patch doesn't fundamentally alter the context of discussion for this.
I was certainly intending that it would. > > Aside from the prospect that people won't really care about group commit > > if they can just use the periodic-WAL-sync approach, ISTM that one way > > to get group commit is to just make everybody wait for the dedicated > > WAL writer to write their commit record. With a sufficiently short > > delay between write/fsync attempts in the background process, won't > > that net out at about the same place as a complicated group-commit > > patch? > > Possibly. To get efficient group commit there would need to be some kind > of signaling between the WAL writer and normal backends. I think there > is some in the patch, but I'm not sure if it gives efficient group > commit. A constant delay will just give us something similar to > commit_delay. Agreed. > I've refrained from spending time on group commit until the > commit-no-wait patch lands, because it's going to conflict anyway. I'm > starting to feel we should not try to rush group commit into 8.3, unless > it somehow falls out of the commit-no-wait patch by accident, given that > we're past feature freeze and coming up with a proper group commit > algorithm would need a lot of research and testing. Better do it for 8.4 > with more time, we've got enough features on plate for 8.3 anyway. My feeling was that I couldn't get both done for 8.3, and that including the WAL Writer in 8.3 would make the dev path clearer for a later attempt upon group commit. I think it was worth exploring whether it would be easy, but I think we can see it'll take a lot of work to make it "fly right". -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings