Ühel kenal päeval, N, 2006-06-29 kell 12:35, kirjutas Tom Lane: > Martijn van Oosterhout <kleptog@svana.org> writes: > >> Tom - what do you think of the other related idea, that of reusing dead > >> index entries ? > > Possibly workable for btree now that we do page-at-a-time index scans; > however I'm pretty hesitant to build any large infrastructure atop that > change until we've got more performance results. We might yet end up > reverting it. > > Another issue is that this would replace a simple hint-bit setting with > an index change that requires a WAL entry. There'll be more WAL traffic > altogether from backends retail-deleting index tuples than there would > be from VACUUM cleaning the whole page at once --- and it won't cut the > I/O demand from VACUUM any, either, since VACUUM still has to scan the > index. AFAICS this wouldn't make VACUUM either cheaper or less > necessary, so I'm not sure I see the point.
How can it generate more traffic ? When you replace a dead index entry with a live one, you just reuse space - you would have to WAL log the index in both cases (adding a new entry or replacing dead entry) Espacially in the case, where you replace an index entryu with the same value. -- ---------------- Hannu Krosing Database Architect Skype Technologies OÜ Akadeemia tee 21 F, Tallinn, 12618, Estonia Skype me: callto:hkrosing Get Skype for free: http://www.skype.com ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
