Re: Free Space Map data structure

PFC wrote:
> 
>     About the FSM :
> 
>     Would it be possible to add a flag marking pages where all tuples 
> are visible to all transactions ? (kinda like frozen I think)

Ah, the visibility map. That's another line of discussion. The current 
plan is to not tie that to the FSM, but implement it separately. There's 
some infrastructure changes that are needed for both, like the "map 
forks" (see recent FSM discussions), which is why we need to have a 
design for FSM as well before we start implementing the visibility map.

It's definitely something I want to do for 8.4. Here's my rough plan:

1. Common "map forks" support
2. Rewrite FSM
3. Implement visibility map, to allow partial vacuums
4. Implement index-only scans, using the visibility map.

We'll see how far I get in the 8.4 cycle. Any help is welcome, of course 
:-).

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com