Re: New FSM patch

On Sep 17, 2008, at 9:30 AM, Heikki Linnakangas wrote:
> I think we'd still need to WAL log operations that decrease the  
> amount of free space on page. Otherwise, after we have partial  
> vacuum, we might never revisit a page, and update the FSM, even  
> though there's usable space on the page, leaving the space  
> forgotten forever.


ISTM that it would be better to deal with such corner cases via  
periodic non-partial vacuums, done by something like autovac, and  
probably done with an ever higher-than-normal vacuum_cost_delay  
setting so as to minimize performance. That's likely a lot less  
wasteful than further compounding lock contention for the WAL. Even  
if it does result in more overall IO, you have to trade a *lot* of IO  
to balance out the impact of lock contention.
-- 
Decibel!, aka Jim C. Nasby, Database Architect  decibel@decibel.org
Give your computer some brain candy! www.distributed.net Team #1828