Re: HOT for PostgreSQL 8.3

On 2/22/07, Zeugswetter Andreas ADI SD <ZeugswetterA(at)spardat(dot)at> wrote:
>
>
> > > 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

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