Greg Stark escribió:
> On Mon, Feb 22, 2010 at 8:18 AM, Gokulakannan Somasundaram
> <gokul007@gmail.com> wrote:
> > a) IOT has both table and index in one structure. So no duplication of data
> > b) With visibility maps, we have three structures a) Table b) Index c)
> > Visibility map. So the disk footprint of the same data will be higher in
> > postgres ( 2x + size of the visibility map).
>
> These sound like the same point to me. I don't think we're concerned
> with footprint -- only with how much of that footprint actually needs
> to be scanned. So if we have a solution allowing the scan to only need
> to look at the index then the extra footprint of the table doesn't
> cost anything at run-time. And the visibility map is very small.
Moreover, the visibility map is already there.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support