Re: HOT patch, missing things

On Thu, 2007-08-09 at 15:46 +0530, Pavan Deolasee wrote:
> 
> 
> On 8/9/07, Simon Riggs <simon@2ndquadrant.com> wrote:
>         
>         Whether I got the exact details of frugging & depruning
>         correct or not:
>         if a tuple version is removed, then VACUUM doesn't need to
>         remove it
>         later, so any non-VACUUM removal of rows must defer a VACUUM.
>         
> 
> 
> ISTM that you are worried about the cases where a tuple is HOT updated
> and hence can be pruned/defragged, but only if we revisit the page at
> a later time.
> 
> What if we just track the amount of potentially dead space in the
> relation 
> (somebody had suggested that earlier in the thread) ? Every committed
> UPDATE/DELETE and aborted UPDATE/INSERT would increment
> the dead space. Whenever page fragmentation is repaired, either during
> normal operation or during vacuum, the dead space is reduced by the 
> amount of reclaimed space. Autovacuum triggers whenever the percentage
> of dead space increases beyond a threshold.
> 
> We can some fine tuning to track the space consumed by redirect-dead
> line pointers.

Sounds great.

--  Simon Riggs EnterpriseDB  http://www.enterprisedb.com