On Thu, 2006-11-09 at 04:09 -0500, Andrew Sullivan wrote: > On Mon, Nov 06, 2006 at 09:50:53PM +0000, Simon Riggs wrote: > > - There are specific issues with the optimizer's ability to understand > > dead row numbers, which can in some cases lead to SeqScan plans that are > > inappropriate when tables grow because of updates. This is a red-herring > > that can lead to people thinking the situation is worse than it is; that > > needs fixing, but the core issues mentioned above remain. > > I don't disagree with much of what you say, but I'm slightly > concerned about the wave-away answer that you give here. In my > experience on high-update tables -- especially ones with the ones > with few rows, but lots of open transactions over the lifetime of the > row -- accurate understanding of dead rows would be a _dramatic_ > improvement (perhaps at least as significant as the improvement being > discussed).
Understood. I just wanted to make sure people understand that the underlying problem would still be there even if we fix that. > That said, I'm not opposed to the line you're taking. I just don't > want this problem to sink forever, because it's a big problem. So, yeh, we should still fix that. The current prototype has a different cost model for SeqScans as a result. Summary arriving anytime now. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq