On Thu, 2007-02-01 at 23:57 -0600, Jim Nasby wrote: > Has anyone actually measured the performance overhead of storing > visibility info in indexes? I know the space overhead sounds > daunting, but even if it doubled the size of the index in many cases > that'd still be a huge win over having to scan the heap as well as > the index (esp. for things like count(*)). There would also be > overhead from having to update the old index tuple, but for the case > of updates you're likely to need that page for the new index tuple > anyway. > > I know this wouldn't work for all cases, but ISTM there are many > cases where it would be a win.
It would prevent any optimization that sought to avoid inserting rows into the index each time we perform an UPDATE. Improving UPDATE performance seems more important than improving count(*), IMHO. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org
