Jan Wieck wrote: > On 6/12/2004 3:45 PM, Tom Lane wrote: > > > Jan Wieck <[EMAIL PROTECTED]> writes: > >> But a per relation bitmap that tells if a block is a) free of dead > >> tuples and b) all remaining tuples in it are frozen could be used to let > >> vacuum skip them (there can't be anything to do). The bit would get > >> reset whenever the block is marked dirty. This would cause vacuum to > >> look at mainly recently touched blocks, likely to be found in the buffer > >> cache anyway and thus dramatically reduce the amount of IO and thereby > >> make high frequent vacuuming less expensive. > > > > I don't think it would help very much to define a bit like that --- I > > can't believe that very many pages would contain only frozen tuples, > > unless you were to adopt an aggressive policy of using VACUUM FREEZE > > a lot. > > I thought this implies an aggressive policy of freezing everything by > default. But I guess there is something I am not aware of that makes > aggressive freezing a bad thing.
Why are frozen tuples significant? I assume any page that has no dead tuples could be skipped by vacuum. -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])