Re: HOT patch, missing things

On Thu, 2007-08-09 at 15:46 +0530, Pavan Deolasee wrote:
>
>
> On 8/9/07, Simon Riggs <simon(at)2ndquadrant(dot)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