>Hannu Krosing [mailto:[EMAIL PROTECTED] > On P, 2004-09-26 at 09:17, Tom Lane wrote: > > "Ross J. Reedstrom" <[EMAIL PROTECTED]> writes: > > > ... So, all this append-only writing leads to files with lots of dead > > > tuples, so the vacuum command was added to reclaim space. > > > > Actually, I believe the original Postgres design envisioned that no > > tuple would ever be permanently deleted: the idea was that you would > > always be able to query the database state as of past times as well > > as the present instant. Stonebraker intended to use the WORM drive as > > the repository for dead tuples that might be needed to answer such > > historical queries. The "vacuum cleaner" was originally a background > > process that pushed dead tuples from magnetic disk to WORM storage. > > We are now getting back to the point where the "background process" part > is true again - how hard would it be to modify vacuum to write recalimed > tuples to somewhere (network pipe, WORM drive, other DB). > > It seems that in addition to writing deleted tuples out to history DB > and making create and delete transaction ids explicitly visible (and do > something(tm) about the transaction id wraparound while at it), the only > thing left to do is some kind of transaction time log - and voila! we > have the original Time Travel feature back - a great feature for > resolving both "audit trail" and "clumsy dba" problems. > > The modern WORM drive equivalent is an IDE(-RAID) disk with its very > tape-like access profile (3+ hours to write full 300GB disk, random > access order(s) of magnitude slower than sequential); > > So if someone is looking for a project, this seems to be something that > is both theoretically possible and also theoretically useful ;) >
Yes, I thought that too - but not for me, not now. Look here: http://research.microsoft.com/db/ImmortalDB/ for similar Best Regards, Simon Riggs ---------------------------(end of broadcast)--------------------------- TIP 3: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
