Re: possible TODO: read-only tables, select from indexes

On Sat, 2005-04-23 at 15:04 -0700, Ron Mayer wrote:
> Bruce Momjian wrote:
> > See this TODO: * Allow data to be pulled directly from indexes 
> > I think this is the direction we should be heading because it has more
> > general usefulness.
> 
> I think read-only tables would have a few different types
> of general usefulness in addition to enabling index scans.
> 
> Is this a fair summary of the potential benefits of READ-ONLY
> tables? (from both this thread and the archives):
> 
>   1.  Index-only scans are made possible fairly easily because
>       you wouldn't need to check the heap for visibility.
> 
>   2.  Simple tables can be much smaller since you don't need
>       most of the HeapTupleHeaderData.   This reduction in
>       space translates to a reduction in I/O through better
>       use of the shared memory and OS caches.
> 
>   3.  A Read-Only Clustered table could be assumed to be
>       sorted, so you could avoid some Sort steps
>       for things like GroupAggregates and Merge Joins.

4. No need to VACUUM tables as part of a database-wide VACUUM, which is
particularly important for larger databases.

Best Regards, Simon Riggs