Re: HOT for PostgreSQL 8.3

Pavan Deolasee wrote:
> On 2/11/07, Hannu Krosing <hannu@skype.net> wrote:
>>
>> Ühel kenal päeval, P, 2007-02-11 kell 12:35, kirjutas Tom Lane:
>> > Hannu Krosing <hannu@skype.net> writes:
>> > > What if we would just reuse the root tuple directly instead of 
>> turning
>> > > it into a stub ?
>> > > This would create a cycle of ctid pointers, which changes the lookup
>> > > process from 'follow ctid chaint until the end' to 'follow the tid
>> chain
>> > > until you reach the start'.
>> >
>> > How do you know which one is newest?
>>
>> By xmin,cmin of course .
> 
> 
> This sounds interesting. But we might have trouble supporting HOT-update
> when
> tuple length changes. May be we can release the space consumed by the dead
> root
> tuple and have fresh allocation if the tuple length increases.

I don't see a problem with length changes. We're free to rearrange data 
on the page whenever we can acquire the vacuum lock.

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