Ühel kenal päeval, N, 2007-03-01 kell 15:03, kirjutas Zeugswetter Andreas ADI SD: > > > > -- start the VACUUM from the first non-filled block > > > > > > > > So if we do this, we wouldn't need to worry about HOT tuples at > all, > > > > nor would we need to wait until all transactions are gone. > > > > > > You need to wait until you are allowed to truncate if you want > > > concurrency. > > > Or a concurrent scan might miss a row, because the visible tuple got > > > > truncated away. > > > > I was not suggesting that we remove visible rows through truncation. > > Sure, unless you suggest to not truncate during this vacuum run ? > But we are talking about vacuum full, so truncation is essential. > > It was suggested to do a dummy null update to move live tuples up front. > The old version is still visible for serializable txns.
There should probably be a wait-other-trxs to finish stage between COMPACT and 2nd VACUUM if truncation at this cycle is absolutely needed > Andreas > > ---------------------------(end of broadcast)--------------------------- > TIP 7: You can help support the PostgreSQL project by donating at > > http://www.postgresql.org/about/donate -- ---------------- 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 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
