Re: Another idea for index-only scans

On Thu, Aug 16, 2007 at 04:06:35PM -0400, Alvaro Herrera wrote:
> 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.

Not for the most common use cases for table partitioning.
--
Decibel!, aka Jim Nasby decibel(at)decibel(dot)org
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