Re: HOT for PostgreSQL 8.3

From: "Pavan Deolasee" <pavan(dot)deolasee(at)gmail(dot)com>
To: "Hannu Krosing" <hannu(at)skype(dot)net>
Cc: "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>, "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>
Subject: Re: HOT for PostgreSQL 8.3
Date: 2007-02-11 18:35:56
Message-ID: 2e78013d0702111035q2058dfbdi1b04fb1ec5667906@mail.gmail.com
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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.

Thanks,
Pavan

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