Tom Lane wrote: > "Heikki Linnakangas" <[EMAIL PROTECTED]> writes: >> Imagine a page with just one tuple on it: > >> 1 > >> After a bunch of updates, it looks like this > >> 1 -> 2 -> 3 -> 4 -> 5 > >> 1 is the tuple the indexes point to, others are heap only. > > But if we were attempting prune at every update, at least some of the > later updates should have managed to prune. "2" should certainly be > gone at this point, unless there's lots of contention for the page, > in which case pruning at select won't make things better.
Oh I see. Yeah, hopefully you don't end up with long chains too often. You don't need contention for it, though, a long-running transaction will cause it. Or a transaction that inserts a tuple and updates it multiple times in the same transaction. -- Heikki Linnakangas EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
