Re: An idle thought

On Fri, 2010-03-19 at 01:59 +0530, Gokulakannan Somasundaram wrote:
> 
>         The visibility map itself is already an example of
>         compression. If
>         visibility information were randomly distributed among tuples,
>         the
>         visibility map would be nearly useless.
>         
>         
> I believe it is very difficult to make visibility map update friendly
> without compromising durability.  But such a functionality is very
> much wanted in PG still.

Surely the VM is already update-friendly. If you update a tuple in a
page with the visibility bit set, the bit must be unset or you will get
wrong results.

Regards,Jeff Davis