Tom Lane wrote: > Christopher Browne <[EMAIL PROTECTED]> writes: > > What is unclear to me in the discussion is whether or not this is > > invalidating the item on the TODO list... > > No, I don't think any of this is an argument against the > dirty-page-bitmap idea. The amount of foreground effort needed to set a > dirty-page bit is minimal (maybe even zero, if we can make the bgwriter > do it, though I'm pretty suspicious of that idea because I think it > needs to be done immediately when the page is dirtied). I don't see the > dirty-page bitmap as changing the way that VACUUM works in any > fundamental respect --- it will just allow the vacuum process to skip > reading pages that certainly don't need to change.
See the email I just posted. I am questioning how big a win it is to skip heap pages if we have to sequentially scan all indexes. > One point that does need to be considered though is what about > anti-wraparound processing (ie, replacing old XIDs with FrozenXID before > they wrap around)? VACUUM currently is a safe way to handle that, > but if its normal mode of operation stops looking at every tuple then > we're going to have an issue there. We would need to do sequential scan occasionally and somehow track that. -- Bruce Momjian http://candle.pha.pa.us SRA OSS, Inc. http://www.sraoss.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
