| From: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
|---|---|
| To: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
| Cc: | Hannu Krosing <hannu(at)skype(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org, Pavan Deolasee <pavan(dot)deolasee(at)enterprisedb(dot)com>, Nikhil S <nikhil(dot)sontakke(at)enterprisedb(dot)com> |
| Subject: | Re: HOT for PostgreSQL 8.3 |
| Date: | 2007-02-11 20:23:55 |
| Message-ID: | 45CF7B5B.8010604@enterprisedb.com |
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| Lists: | pgsql-hackers |
Pavan Deolasee wrote:
> On 2/11/07, Hannu Krosing <hannu(at)skype(dot)net> wrote:
>>
>> Ühel kenal päeval, P, 2007-02-11 kell 12:35, kirjutas Tom Lane:
>> > Hannu Krosing <hannu(at)skype(dot)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
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