Re: Another idea for index-only scans

On Wed, 2007-08-15 at 11:54 -0400, Bruce Momjian wrote:
> I have added another idea for index-only scans to the TODO list:
>
> > A third idea would be for a heap scan to check if all rows are visible
> > and if so set a per-table flag which can be checked by index scans.
> > Any change to the table would have to clear the flag. To detect
> > changes during the heap scan a counter could be set at the start and
> > checked at the end --- if it is the same, the table has not been
> > modified --- any table change would increment the counter.
>

This sounds useful for read-only or read-mostly tables.

However, it also sounds a little dangerous. If you test your application
performance, but not thoroughly enough, you might end up with a surprise
when going into production.

Regards,
Jeff Davis