Hannu Krosing wrote: > ?hel kenal p?eval, N, 2006-07-27 kell 22:05, kirjutas Bruce Momjian: > > Another idea Jan had today was whether we could vacuum more rows if a > > long-running backend is in serializable mode, like pg_dump. > > I don't see how this gives us ability to vacuum more rows, as the > snapshot of a serializable transaction is the oldest one.
Good question. Imagine you have a serializable transaction like pg_dump, and then you have lots of newer transactions. If pg_dump is xid=12, and all the new transactions start at xid=30, any row created and expired between 12 and 30 can be removed because they are not visible. For a use case, imagine an UPDATE chain where a rows was created by x=15 and expired by xid=19. Right now, we don't remove that row, though we could. -- Bruce Momjian [EMAIL PROTECTED] EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
