On 22 Aug 2003 at 10:45, Tom Lane wrote: > Jan Wieck <[EMAIL PROTECTED]> writes: > > Shridhar Daithankar wrote: > >> Umm.. What does FSM does then? I was under impression that FSM stores page > >> pointers and vacuum work on FSM information only. In that case, it wouldn't > >> have to waste time to find out which pages to clean. > > > It's the other way around! VACUUM scan's the tables to find and reclaim > > free space and remembers that free space in the FSM. > > Right. One big question mark in my mind about these "partial vacuum" > proposals is whether they'd still allow adequate FSM information to be > maintained. If VACUUM isn't looking at most of the pages, there's no > very good way to acquire info about where there's free space.
Somehow it needs to get two types of information. A. If any transaction is accessing a page B. If a page contains any free space. Vacuum needs to look for pages not in A but in B. Can storage manager maintain two lists/hashes with minimal cost? In that case, all unlocked and not in transaction pages could be a much smaller subset. Does it sound bizzare? Bye Shridhar -- Chemicals, n.: Noxious substances from which modern foods are made. ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
