On Tue, Dec 26, 2006 at 07:22:21PM +0100, Martijn van Oosterhout wrote: > On Tue, Dec 26, 2006 at 12:49:55PM -0500, D'Arcy J.M. Cain wrote: > > On Tue, 26 Dec 2006 18:12:45 +0100 > > Martijn van Oosterhout <kleptog@svana.org> wrote: > > > On Tue, Dec 26, 2006 at 12:04:40PM -0500, D'Arcy J.M. Cain wrote: > > > > Now it certainly seems to me that it should behave as described given > > > > the definition of VACUUM FULL so I am a little confused by my tests. > > > > My test table only has two entries in it. Is that the issue? In fact, > > > > I find the same behaviour if I do a simple VACUUM on the table. > > > > > > On a table with two entries, VACUUM FULL is going to do nothing of > > > interest. Moving tuples within a page is useless, generally. > > > > I thought that that might be the issue. The docs should probably say > > "can" instead of "will" then. > > The doumenttion is accurate as is. It says when "moved by VACUUM FULL". > In your case they wern't moved. If you change the word "will" to "can", > it will be wrong.
Howso? There's no guarantee (which is what "will" implies) that a ctid will change on VACUUM FULL. In fact, your example demonstrates that; 0,1 stayed put. I'm sorry if it sounds like I'm picking nits, but using CTID to identify rows could provide a noticeable performance gain in some cases. But users can't make use of that if it's not clear exactly when and how CTIDs can change. -- Jim Nasby [EMAIL PROTECTED] EnterpriseDB http://enterprisedb.com 512.569.9461 (cell) ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
