Re: HOT for PostgreSQL 8.3
| От | Pavan Deolasee |
|---|---|
| Тема | Re: HOT for PostgreSQL 8.3 |
| Дата | |
| Msg-id | 2e78013d0702220407p204c6a0bt7b6734d04c6a40fd@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: HOT for PostgreSQL 8.3 ("Zeugswetter Andreas ADI SD" <ZeugswetterA@spardat.at>) |
| Ответы |
Re: HOT for PostgreSQL 8.3
|
| Список | pgsql-hackers |
On 2/22/07, Zeugswetter Andreas ADI SD <ZeugswetterA@spardat.at> wrote:
Hannu talked about using one of xmin/xmax for storing
back-pointers. There were objections to that since it breaks
the xmax/xmin matching robustness that we have today.
> > I very much like Hannu's idea, but it does present some issues.
> >
> >
> I too liked Hannu's idea initially, but Tom raised a valid
> concern that it does not address the basic issue of root
> tuples. According to the idea, a DEAD root tuple can be used
> for a subsequent update of the same row.
If you are reusing the existing slot of a root tuple how will that
slot likely have room for an extra pointer and a live tuple ?
If the idea does not cover root reuse we don't need pointers.
Hannu talked about using one of xmin/xmax for storing
back-pointers. There were objections to that since it breaks
the xmax/xmin matching robustness that we have today.
Imho we should follow the swing idea.
Yes, thats one option. Though given a choice I would waste
four bytes in the heap-page than inserting a new index entry.
The heap tuples can be vacuumed rather easily than the index
entries which, if I am mistaken, can not be reused even after
marked LP_DELETEd.
Thanks,
Pavan
--
EnterpriseDB http://www.enterprisedb.com
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