Jeff Davis wrote:
> 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.
I think it's too coarse-grained to be really useful. If it was one bit
per page it could work, but one bit per relation is going to be reset
too frequently.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
