| From: | Hannu Krosing <hannu(at)skype(dot)net> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | 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 18:16:22 |
| Message-ID: | 1171217782.3618.31.camel@localhost.localdomain |
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| Lists: | pgsql-hackers |
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 .
> What happens when you have to put a newer version off-page for lack of space?
Then this scheme won't work.
How about adding a new 2-byte field to header for in-page c_tid poiner
for HOT ?
It grows header from 26 to 28 bytes, but for MAXALIGN=4 the space usage
would stay the same.
> regards, tom lane
--
----------------
Hannu Krosing
Database Architect
Skype Technologies OÜ
Akadeemia tee 21 F, Tallinn, 12618, Estonia
Skype me: callto:hkrosing
Get Skype for free: http://www.skype.com
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